Double Pen Up Event

1. Field of the Invention

The present invention relates to a pen-based computer system and more particularly to a pen-based wireless interface device that can emulate a standard mouse function with a passive stylus which generates a plurality of mouse data packets for each pen up event to prevent maloperation of the system in the event the data packet for the pen up event is lost or garbled.

2. Description of the Prior Art

Pen-based portable personal computer systems are generally known in the art. Such systems typically include a digitizer panel and a pen controller and utilize a stylus as an input device. The pen controller normally generates a series of interrupts and, in turn, a series of packets whenever the stylus touches or is lifted from the digitizer panel. The x-y coordinates of each pen down event are generated as a series of four 8-bit packets (p1, p2, p3, p4). Pen up data is generated as a single packet p5. In certain conditions, the interrupts are disabled in order to enable the pen packets to be processed. During the time when the interrupts are disabled, the x-y coordinate packets (p1, p2, p3, p4), as well as the pen up packet p5, are not processed and thus can become garbled or lost. Since mouse emulation is based on both pen-down and pen-up events, lost pen-up packets p5 can result in the mouse emulation being hampered, possibly resulting in the system being stuck in the state preceding the pen-up event.

It is an object of the present invention to solve various problems in the prior art.

It is yet another object of the present invention to provide a pen-based computer system that includes a digitizer and a passive stylus which can emulate a standard two-button mouse.

Briefly, the present invention relates to a pen-based computer system device and more particularly to a pen-based computer system with a digitizer which utilizes a passive stylus as an input device. The system emulates standard two-button mouse functions by generating data packets corresponding to the x-y coordinates of the stylus for each pen-down event. In order to prevent malfunction of the system, a plurality of packets are generated for each pen-up event to prevent maloperation of the system in the event a data packet for a pen-up event is lost or garbled.

These and other objects of the present invention will be readily understood upon consideration of the following detailed description and attached drawing, wherein:

FIG. 1 is a block diagram of the hardware configuration of a wireless interface device in accordance with the present invention and a host computer;

FIG. 2 is a block diagram illustrating the access of the wireless interface device in accordance with the present invention and a wired local area network;

FIG. 3 is a diagram illustrating the software structure for the wireless interface device in accordance with the present invention;

FIG. 4 is a block diagram showing one implementation of the wireless interface device of FIG. 1;

FIG. 5 is a state diagram illustrating the six internal power management states of the wireless interface device;

FIG. 6 is a block diagram illustrating the operational states of the wireless interface device under the control of dedicated Viewer Manager software in accordance with the present invention;

FIG. 7 is a block diagram of the software environment under which the wireless interface device and the host computer operate to provide remote control of the host computer;

FIG. 8 is a block diagram which shows in further detail the software environment in the host computer, running an application program under a Windows environment;

FIG. 9 is a block diagram which shows in further detail the software environment in the wireless interface device, running in a normal operation state;

FIG. 10 is a block diagram illustrating the method used in the wireless interface device to anticipate a pen/mouse mode decision;

FIGS. 11-30 are schematic diagrams of the wireless interface device in accordance with the present invention;

FIGS. 31-35 are flow charts relating to mouse emulation with a passive pen;

FIG. 36 is a plan view of the wireless interface device illustrating the hot icon area and viewing area of the display;

FIG. 37 illustrates the hot icons in the hot icon area of the display;

FIGS. 38, 39 and 40 are flow charts relating to a system for disabling the screen saver to reduce LAN traffic;

FIG. 40A is a flow chart relating to a host access protection password system;

FIGS. 41-43 are flow charts relating to a system for handling pen-up events;

FIG. 44 is a configuration diagram illustrating the wireless interface device interfacing with a wired LAN system;

FIG. 45 is a diagram of the software structure of a known network system;

FIG. 46 is a diagram of the software structure of network system which enables the wireless interface device to interface with the wired LAN system, illustrated in FIG. 44;

FIGS. 47-52 are flow charts relating to the seamless integration of wired and wireless LANS;

FIGS. 53-57 are illustrations of various set-up dialog boxes available on the wireless interface device;

FIG. 58 is a flow chart relating to the host control mode;

FIG. 59 is a flow chart relating to a system for broadcasting for available hosts;

FIGS. 60 and 61 are flow charts relating to a system for providing remote keyboard macros on the wireless interface device;

FIGS. 62 and 63 are flow charts relating to a wireless flash ROM programmer;

FIGS. 64A and 64B are flow charts relating to a system for providing automatic reconnection of the host;

FIGS. 65A and 65B are flow charts relating to providing a remote occlusion region on the wireless interface device; and

FIGS. 66A-66D illustrate the various configurations of an on-screen keyboard available on the wireless interface device.

The present invention relates to a system which allows wireless access and control of a remote host computer, which may be either a desktop, tower or portable computer to enable remote access of the various files and programs on the host computer. The system not only allows access to remote host computers that are configured as stand-alone units but also provides access to both wired and wireless local area networks (LAN).

The system includes a wireless interface device which includes a graphical user interface (GUI) which allows various types of input. In particular, input to the wireless interface device is primarily by way of a passive stylus, which can be used in a pen mode or a mouse mode. In a pen mode, a trail of ink tracking the path of the stylus (pen paradigm) provides visual feedback to the user by way of a pen digitizer. In a mouse mode, however, a cursor may be generated which follows the "tip" of the pen, but the path of cursor motion is not inked.

A virtual keyboard is also provided as part of the GUI. Activation of the keys on the virtual keyboard is by way of the stylus or by finger input. In addition, the system also supports a full-size external keyboard.

FIG. 1 illustrates a block diagram of the system in accordance with the present invention. In particular, a wireless interface device 100, in accordance with the present invention, enables wireless access of a remote host computer 101, configured as either a stand-alone unit or as a part of a wired or wireless local area network (LAN). When the remote host computer 101 is in a stand-alone configuration, as illustrated in FIG. 1, communication between the remote host computer 101 and the wireless interface device 100 is by way of a wireless communication link, provided by a communication subsystem 118 in which the remote host computer 101 is provided with a transceiver 115 for radio communication with a transceiver 116 in the wireless interface device 100. For example, the desktop or remote host computer 101 can be provided with a PCMCIA interface which can be used with a wireless transceiver card to communicate with the transceiver 116 in the wireless interface device 100. Alternatively, an Industry Standard Architecture (ISA) card transceiver can be installed in the host computer 101 in a spare ISA expansion slot. In particular, the transceivers 115 and 116 may be implemented as 2.4 GHz radio frequency (RF) transceiver modules with a Wireless Media Access Control function, available from Proxim Inc., Mountain View, California, configured with either an ISA or PCMCIA interface.

As mentioned above, the wireless interface device 100 can also be used with a wireless LAN in a peer-to-peer network or a wired LAN. FIG. 2 illustrates the communication between the wireless interface device 100 and a wired LAN 114, which includes a server 108 in a, for example, Novell Netware or Microsoft LAN Manager environment. In this mode, the transceiver 116 in the wireless interface device 100 communicates with an access point 109 by way of a transceiver (not shown), which interfaces the wireless interface device 100 with a wired LAN 114 which includes a server 108. Alternatively, the wireless interface device 100 can be used in a wireless network in a Windows for Workgroups or Personal Netware environment, for example.

The configuration of the radio communication subsystem between the wireless interface device 100 and the remote host computer 101 or access point 109 conforms to the Open System Interconnection (OSI) reference model for data communications and implements the lower two layers of the seven-layer OSI model. In particular, with reference to FIG. 3, the physical layer 107 (WIRELESS PHY) may be a 2.4 GHz spread spectrum frequency hopping radio which replaces the LAN cable normally connected between workstations. The radio operates within the 2.4000-2.4835 GHz band, the unlicensed Industrial Scientific and Medial (ISM) band, and is divided into eighty-two 1 MHz channels. In a spread-spectrum, frequency-hopping radio, data is broadcast on one particular channel for a predetermined time (i.e. 400 msec); and then the system hops to another channel in a predetermined pattern to avoid interference.

The wireless media access control (WIRELESS MAC) 106 is used to interface to higher level software 105 (i.e. NOS SHELL, NOVELL, MICROSOFT) through network drivers 104 (i.e. LINK LEVEL INTERFACE (ODI, NDIS)). The MAC conforms to the industry standard protocol is in accordance with IEEE 802.11.

As shown in FIG. 1, the wireless interface device 100 includes a central processing unit (CPU) 112, a local memory system 111, a pen-based input subsystem (STYLUS) 110, a display subsystem 113 and a transceiver 116. As will be discussed in more detail below, the wireless interface device 100 includes a Viewer Manager software 200 (FIG. 6) which performs three (3) basic functions: (i) collecting and transmitting input positional information from a stylus input subsystem 110 to the host computer 101, (ii) receiving from the host computer 101 a video image to be displayed on the display subsystem 113, and (iii) managing the communications link between the wireless interface device 100 and the host computer 101.

The wireless interface device 100 is thus able to control and access various programs such as Windows and Windows application programs and files residing at the host computer 101 and display the results in its display 113.

FIG. 4 is a block diagram of the wireless interface device 100. As shown in FIG. 4, the wireless interface device 100 has both a processor or "local bus" 150 and an ISA bus 151. The local bus 150 operates at the clock rate of the CPU 112, while the ISA bus 151 operates at the industry standard 8 MHz clock rate. The CPU 112 may be implemented by a microprocessor, which allows suspension and resumption of operation by halting and restarting the system clock to reduce battery consumption. Because power management in a portable device is important, the CPU 112 should preferably support power management functions, such as System Management Mode (SMM) and System Management Interrupt (SMI) techniques known in the industry. One example of a suitable microprocessor is the AMD386DXLV, available from Advanced Micro Devices, Inc., Sunnyvale, Calif., which operates at up to 25 MHz at a 3.0V supply voltage.

The CPU 112 interfaces over local bus 150 with a system controller 129. The system controller 129 manages (i) system operation, including the local and ISA buses 150 and 151, (ii) memory, and (iii) power to the system. The system controller 129 may be, for example, a Model No. 86C368 integrated circuit, available from PicoPower Technology, Inc., San Jose, Calif.

The present implementation takes advantage of the several levels of power management supported by the system controller 129. Power management in the present implementation is described in further detail below.

The system controller 129 provides a dynamic random access memory (DRAM) controller and a non-volatile random access memory (NVRAM) controller to control the DRAM 111A and a non-volatile RAM, NVRAM 111B, which form a portion of the memory subsystem 111 (FIG. 1) in the wireless interface device 100. As shown in FIG. 4, the DRAM 111A in the wireless interface device 100 may be provided by four 16-bit by 256K DRAM memory chips, to provide a total of 2 megabytes of memory, while the NVRAM 111B, used to store configuration data and passwords, for example, may be implemented using E.sup.2 PROM technology to provide permanent storage.

All devices on the ISA bus 151 are managed by an integrated peripheral controller (IPC) 128. The IPC 128 provides various functions including direct memory access (DMA) control, interrupt control, a timer, a real time clock (RTC) controller, and a memory mapper for mapping peripheral devices to the system memory space as illustrated in Table 4 below. The IPC 128 may be implemented by a Model No. PT82C206 integrated circuit, also available from the aforementioned PicoPower Technology, Inc.

The stylus input subsystem 110 is implemented by a stylus, a pen controller 110A and a digitizer panel 110B. The pen controller 110A controls the digitizer panel 110B and provides positional information of pen or stylus contact. The pen controller 110A can be implemented, for example by a Model No. MC68HC705J2 microcontroller, available from Motorola, Inc. In this implementation, the digitizer panel 110B can be, for example, an analog-resistive touch screen, so that the stylus is sensed by mechanical pressure. Using a digitizer panel which senses mechanical pressure allows a "dumb" stylus, or even the human finger, to be used as an input device. When using a dumb stylus, switching between mouse and pen modes is accomplished by selecting an icon as discussed below. Alternately, other styli, such as a "light pen" or an electronic stylus with various operating modes, can also be used. In some electronic stylus', switching between pen and mouse modes can be achieved by pushing a "barrel button" (i.e. a switch located on the barrel of the stylus).

As mentioned above, the wireless interface device 100 includes a display subsystem 113 which, in turn, includes a liquid crystal display (LCD) 113C. The LCD 113C is controlled by a video controller 113A, and supported by video memory 113B. The video controller 113A can be implemented by a Model No. CL-GD6205 video controller, available from Cirrus Logic Corporation, Milpitas, Calif. The LCD 113C can be, for example, a monochrome display, such as the Epson EG9015D-NZ (from Epson Corporation), or an active matrix color display. The video memory 113B may be implemented as DRAMs, organized as 256K by 16 bits.

The video controller 113A communicates with video memory 113B over a separate 16-bit video bus 113D. In this implementation, the video controller 113A provides "backlighting" support through a backlight control pin BACKLITEON that is de-asserted to conserve power under certain power management conditions as discussed below.

As discussed above, the communication subsystem 118 allows communication with a remote host computer 101 in either a stand-alone configuration or connected to either a wired or wireless LAN. The communication system 118 includes the transceiver 116, an antenna 116A, and an RF controller 114A for interfacing with the local ISA bus 151.

The wireless interface device 100 also includes a keyboard controller 125 which performs, in addition to controlling an optional keyboard by way of a connector, various other functions including battery monitoring and LCD status control. The keyboard controller 125 can be implemented by a Model No. M38802M2 integrated circuit from Mitsubishi Corporation, Tokyo, Japan. Battery power to the wireless interface device 100 may be provided by an intelligent battery pack (IBP) 131, for example, as described in U.S. patent application Ser. No. 07/975,879, filed on Nov. 13, 1992, hereby incorporated by reference, connected to a system power supply module 133 by way of a battery connector 132. The IBP 131 maintains and provides information about the remaining useful battery life of IBP 131, monitored by keyboard controller 125. Upon the occurrence of a significant event relative to the IBP 130, e.g. battery remaining life falling below a preset value, the keyboard controller 125 generates an interrupt signal.

A serial port is provided and implemented by way of a universal asynchronous receiver transmitter (UART) 134, which can be accessed externally via a serial port connector 135. As will be discussed in more detail below, the serial port connector 135 allows for disaster recovery for the flash memory 117, which may be used to store the basic input/output (BIOS) for the CPU 112.

In order to conserve battery power, the wireless interface device 100 incorporates power management. While a user of the wireless interface device 100 would normally only be aware of four power management states: "off"; "active"; "suspend"; and "sleep" modes, internally six power management states are implemented as shown in FIG. 5. More particularly, with reference to FIG. 5, before the wireless interface device 100 is powered up, the wireless interface device 100 is in an "off" state, indicated by the reference numeral 160. In an "off" state 160, no power is supplied to the system. A state 161 (the "active" state) is entered when the power switch (FIG. 28) to the wireless interface device 100 is turned to the "on" position. In the active state 161, all components of wireless interface device 100 are active. From active state 161, the wireless interface device 100 enters a "local standby" state 162. The local standby state 162 is transparent to the user of the wireless interface device 100. From the user's point of view, in the local standby state 162, the wireless interface device 100 is in active mode. In this state 162, specific inactive devices are each put into a static state after a predetermined time-out period of inactivity for that device. In a static state, each device consumes minimal power. In the local standby state 162, devices that can be put into static states include the CPU 112, the video controller 113A, the pen controller 110A, the UART 134, and the transceiver 116. Backlighting of the LCD video display is also disabled in local standby state 162. If not, input activities are detected by the keyboard controller 125 or pen controller 110A. After the later of their respective present time-out periods, these devices are placed in a static state. These devices emerge from the static state once an activity relevant to its operation is detected, e.g. a pen event is detected.

The user of the wireless interface device 100 can place the wireless interface device 100 in a "sleep" mode 163 by selecting an icon (FIG. 37) labelled "sleep" from the GUI as will be discussed below. Alternatively, the "sleep" mode may be entered from the active state 161 after a preset period of inactivity. In a "sleep" mode, corresponding to either "sleep" state 163 or "active sleep" state 164, the display subsystem 113 is switched off; and most devices are placed in static states. When a keyboard or pen event is detected, the sleep state 163 and active sleep state 164 are exited, and the wireless interface device 100 enters the active state 161. From the sleep state 163, an active sleep state 164 is entered when a communication packet is received from the host computer 101. Although the display subsystem 113 is turned off, the received communication packet can result in an update to an image stored in the video memory 113B. The CPU 112 handles the communication packet from the host computer 101 and activates the video controller 113A to update such an image. The active sleep state 164 is transparent to the user of the wireless interface device 100, since the updated image is not displayed on the LCD screen 113C. When the communication packet is handled, the wireless interface 100 returns to a sleep state 163. The device activities in wireless interface device 100 in "sleep" mode 163 are illustrated in Table 1 below.

Upon expiration of a timer, the wireless interface device 100 enters into an internal state "suspend" mode 165. In a suspend mode, the wireless interface device 100 is essentially turned off and communication packets from the host computer 101 are not handled. The wireless interface device 100 emerges from suspend state 165 into active state 161 when a pen event is detected.

As mentioned above, the video controller 113A supports various power management modes internal to the display subsystem 113. Power is conserved in display subsystem 113 by entering "standby" and "suspend" modes. In the video controller 113A's "standby" mode, which can be entered by (i) expiration of a timer internal to the video controller 113A, (ii) firmware in the video controller 113A, or (iii) a signal received from system controller 129 on the video controller 113A's "STANDBY" pin. In the video controller 113A's standby mode, the LCD 113C is powered down and the video clock is suspended. The video controller 113A exits the standby mode either under firmware control, or upon system controller 129's de-asserting video controller 113A's STANDBY pin. Upon exiting standby mode, the LCD 113C is powered and the video clock becomes active. In this implementation, the LCD 113C includes multiple power planes ("panels"). For reliability reasons, in a powering up or powering down operation, these panels in the LCD display are preferably powered in a predetermined sequence specified by the manufacturer.

Maximum power is conserved in the display subsystem 113 when video controller 113A enters the "suspend" mode. The suspend mode can be entered either by asserting a signal from the system controller 129 on the SUSPEND pin of video controller 113A, or under firmware control. In this implementation, if the suspend mode is entered from the SUSPEND pin, the CPU 112 is prevented from accessing the video RAM 113B and video bus 113D. In that state, the contents of configuration registers in the video controller 113A are saved, to be restored when suspend mode is exited. In the suspend mode, the video RAM 113B is refreshed using the lowest possible refresh clock rate.

FIG. 6 is a block diagram illustrating the operational states of wireless interface device 100 under the control of the Viewer Manager software 200. As shown in FIG. 6, on power up, the wireless interface device 100 enters into a "TABLET SECURITY" state 201, in which an optional security step is performed. In the state 201, either the device 100 automatically shuts off after an idle period or the user performs a "log on" procedure which, as a security measure, identifies and validates the user. Then, at decision point 202, the Viewer Manager software 200 then determines if a procedure to set up a communication link is preconfigured. If so, a communication link is established automatically with the host computer 101 and the Viewer Manager software 200 goes into the normal operation state 205, which is described in further detail below. If a communication link is not preconfigured, a manual procedure is performed in state 203, in which the desired host computer 101 is identified and connected. From state 203, either the device 100 automatically shuts off after an idle period or the user continues on and enters normal operation state 205.

In normal operation state 205, the wireless interface device 100 controls the program running in the host computer 101, in accordance with the input data received from stylus input subsystem 110. The positions of the stylus in stylus input subsystem 110 are delivered to the host computer 101, which generates display commands to the wireless interface device 100. The CPU 112 executes the display commands received, which may result in an update of the LCD 113C. In this embodiment, either a direct user command or inactivity over a predetermined time period causes the wireless interface device 100 to enter a "HOT-STANDBY" minimum power state ("sleep" mode), represented in FIG. 6 by block 204. In the minimum power state 204, to preserve battery power, the various operations of the wireless interface device 100's functional units are placed on standby status. If the status is put in contact with the digitizer panel, the wireless interface device 100 is reactivated, and control of the host computer 101 is resumed by re-entering state 205. Thereupon, wireless interface device 100 enters into a state 206, in which an auto-disconnect procedure is executed, which releases control of the host computer 101 and powers down the wireless interface device 100.

The user may also relinquish control of the host computer 101 from state 205 by selecting a manual disconnect function. When the manual disconnect function is selected, the wireless interface device 100 enters manual disconnect state 207, in which the connection to the host computer 101 is terminated. The wireless interface device 100 is then returned to state 201 to accept the next user validation.

FIG. 7 is a block diagram of the software environment 240 in which the wireless interface device 100 and the host computer 101 operate to provide the wireless interface device 100 remote control of the host computer 101. As shown in FIG. 7, a wireless communication system 250 is provided for communication between the host computer 101 and the wireless interface device 100. On the side of the wireless interface device 100, i.e. software environment 230A, a communication output manager software routine 252 controls transmissions of pen events over the wireless communication link 250 to a host communication input manager 262 in the host computer 101 (i.e. software environment 230B). The pen events include the position information of the stylus and tip-up and tip-down information. A pen event buffer 251 queues the pen events for transmission through a communications manager 252. In the software environment 230A, the communications input manager 254 receives from the wireless communication system 250 video events transmitted by host communication output manager 260 in the software environment 230B. These video events include graphical commands for controlling the LCD 113C. In the software environment 230A, the received video commands are queued in the video event buffer 256 to be processed by the CPU 112 as graphical instructions to the LCD 113C.

In the software environment 230B, i.e. in host computer 101, pen events are queued in pen event buffer 264, which may then be provided to the Pen Windows module 266. The Pen Windows module 266 processes the pen events and creates video events in a video event buffer 267, which is then transmitted to the wireless interface device 100 over wireless communication system 250.

FIG. 8 is a block diagram which shows in further detail the software environment 230B (FIG. 7) in the host computer 101; running an application program 270 under a Windows operating system 272. As shown in FIG. 8, the pen events queued in the pen event buffer 264 are provided to a pen event injector 274, which provides the pen events from the pen event buffer 264, one pen event at a time, to a buffer ("RC buffer") 275 of the Recognition Context Manager module (the "RC manager") 276 in Pen Windows. The RC buffer 275 holds a maximum of four pen events. The RC Manager 276 assumes that pen events are received at RC buffer 275 as they occur. Thus, if the Pen Windows system is presented with pen events faster than they are retrieved from RC buffer 275 without pen event injector 274, the pen events that arrive at RC buffer 275 when it is full are lost. The pen event injector 274 prevents such data loss. To provide this capability, the pen event injector 274 includes both Windows virtual device (V.times.D) and device driver (DRV) codes (not shown). The DRV portion removes a single pen event from pen event buffer 264 and delivers it to the RC buffer 275 using the normal Pen Windows add and process pen event mechanisms. Then the V.times.D portion reactivates the DRV code after a minimum time delay using a virtual machine manager service to retrieve the next pen event from pen event buffer 264. Those of ordinary skill in the art would appreciate that, under the terminology used in Windows, DRV code refers to a dynamically linked library in Windows which interacts with a hardware device (in this case, pen device buffer 264), and V.times.D code refers to a dynamically lined library which manages a sharable resource (in this case, the DRV code).

The RC Manager 276 examines each pen event in the RC buffer 275, and according to the context of the pen event in its possession, the RC Manager 276 determines whether the stylus is in the pen mode or in the mouse mode. In this embodiment, as will be discussed in more detail below, an icon allows the user to use the stylus as a "mouse" device. The icon, called "mouse button toggle", allows the user to switch between a "left" button and a "right" button as used in an industry standard mouse device. The selected button is deemed depressed when the stylus makes contact with the pressure-sensitive digitizer panel. A rapid succession of two contacts with the display is read by the RC Manager 276 as a "double click", and dragging the stylus along the surface of the display is read by the RC Manager 276 as the familiar operation of dragging the mouse device with the selected button depressed.

If the stylus is in the pen mode, the RC Manager 276 provides the pen event to a recognizer 277 to interpret the "gesture". Alternatively, if the pen event is a mouse event, the RC Manager 276 provides the pen event as a mouse event for further processing in a module 278. The interpreted gestures or mouse events are further processed as input data to the Windows operating system 272 or the application program 270.

The output data from an application program, such as Windows 272 or application program 270, is provided to the video event buffer 267. These video events are transmitted to the host communications output manager 260 for transmission to the wireless interface device 100.

FIG. 9 is a block diagram which shows in further detail the software environment 230A in the wireless interface device 100 in the normal operation state 205 of the Viewer Manager 200. In FIG. 9, the stylus in the stylus input subsystem 110 and LCD video display 113C in the video display subsystem 113 are shown collectively as a digitizer-display device 279. In a normal operation state 205, the Viewer Manager 200 interacts with the application program 270 in the wireless interface device 100 by way of the Communications Output Manager 252 and the Communications Input Manager software 254. In addition, the Viewer Manager software 200 also receives digitized data from a digitizer 280, which, in turn, receives digitized data from stylus input subsystem 110. The Viewer Manager software 200 uses the digitized data to provide visual feedback to the user, which is discussed in further detail below. The Viewer Manager software 200 generates local video commands to a display driver 281. The display driver 281 also receives from video event buffer 256 video display commands from the host computer system 101.

At the core of the wireless interface device 100's user interface is the stylus's behavior under Pen Windows. Of significance in wireless interface device 100's design is the emulation of the natural "pen-and-shaper" interaction with the user. That is, in a pen mode, the stylus must leave ink as it moves across the surface of the screen in the same way that a pen leaves ink on paper. However, using Pen Windows software, the RC Manager 276, residing in the host computer 101, determines for each pen event whether the mouse or the pen mode is used.

If the wireless interface device 100 simplistically accesses the host computer 101 as a local device access, the wireless link between the host computer 101 and the wireless interface device 100 would be required to carry a minimum of 200 inking messages per second (100 stylus tip locations plus 100 line drawing commands). To maintain the pen-and-paper emulation, the wireless interface device 100 is further required to have a total processing delay (hence response time), including the overhead of the communication protocols, which is near or below the human perception level. In addition, noise in the transmission medium often leads to momentarily interruption of data transmission, or results in data corruption that requires re-transmission, thereby further reducing the throughput of the wireless link. To provide an acceptable level of performance, i.e., a high message-per-second communication rate and an acceptable propagation delay, a technique referred to as "local inking" is developed and applied to the wireless interface device 100's design, in accordance with the present invention. Without local inking, a high bandwidth communication link is required to meet the propagation delay requirement. Such a high bandwidth communication link is impractical, both in terms of cost and its impact on the portability of the resulting wireless access device.

With local inking, the Viewer Manager software 200 provides inking on the LCD 113C locally before the corresponding inking video events are received from the host computer 101. In this manner, visual feedback is provided virtually immediately without requiring either highly complex networking equipment, or very high performance and costly components in both the wireless interface device 100 and the host computer 101. Local inking provides both a real time response and an orderly handling of the stylus's data stream. Since local inking reduces the need for processing at the peak pen event rate of the stylus's data stream, the host computer 101 can thus apply normal buffering techniques, thereby reducing the bandwidth requirement on the communication network.

In one proposed industry standard for a stylus or pen-based system, namely the Microsoft Windows for Pen Computing system ("Pen Windows"), the pen mode requires (i) a pen driver that can deliver stylus tip locations every five to ten milliseconds (100 to 200 times per second), so as to achieve a resolution of two hundred dots per inch (200 dpi), and (ii) a display driver than can connect these dots in a timely manner. By these requirements, Pen Windows attempts to provide a real time response to maintain the pen paradigm. The Windows for Pen Computing system is promoted by Microsoft Corporation, Redmond, Wash. Details of the Pen Windows system are also provided in Windows version 3.1 Software Developer Kit obtainable from Microsoft Corporation. Under one implementation of the Pen Windows, a maximum of four stylus locations can be stored in a buffer of a module called "PENWIN.DLL" (for "Pen Window Dynamically Linked Library")). Consequently, in that implementation, the maximum latency allowed is twenty to forty milliseconds before any queue tip location is written. Each time the system fails to process a pen event within twenty to forty milliseconds of queuing, a stylus tip location is lost and there is a corresponding impact on the accuracy of the line being traced.

As mentioned above, the stylus is used in both pen mode and mouse mode. Since the RC Manager 276, running on the host computer 101, rather than a software module on the wireless interface device 100, determines whether a given pen event is a mouse mode event or a pen mode event, the Viewer Manager software 200 must anticipate which of these modes is applicable for that pen event. Further, should the anticipated mode prove to be incorrect, the Viewer Manager software 200 is required to correct the incorrectly inked image in video display subsystem 113.

FIG. 10 illustrates the method used in the wireless interface device 100 to anticipate the RC Manager 276's mode decision and to correct the image in the video display subsystem 113 when a local inking error occurs. As shown in FIG. 10, when the normal operational state 205 is entered, a pen control program (represented by the state diagram 282) in the Viewer Manager software 200 is initially in the mouse mode in state 283. However, even in the mouse mode, the trajectory of the stylus in contact with the pen digitizer is stored in the pen event buffer 284 until a mode message is received from the host computer 101. The pen event buffer 284 is separate from pen event buffer 251, which is used to transmit the pen events to the host computer 101. If the RC Manager 276 confirms that the stylus 110 is in a mouse mode, the accumulated pen events are discarded and the pen control program 282 waits for the last point on which the pen tip is in contact with the pen digitizer. Then the pen control program 282 returns to a state 283, in which the trajectory of the pen is again accumulated in the pen event buffer 284 until receipt of a mode message from the host computer 101. In state 283, the control program 282 assumes that the stylus will continue to be in the mouse mode.

Alternatively, while in state 283, if a mode message is received indicating the stylus is in the pen mode, the control program 282 enters state 288, in which the accumulated pen events are drawn locally onto the LCD screen of the video display subsystem 113 in accordance with the line style and color specified in the mode message. After all accumulated pen events in the pen event buffer 284 are drawn, the control program 282 enters a state 289, in which control program 282 continues to ink the trajectory of the tip of the stylus for as long as contact with the pen digitizer is maintained. Once the tip of the stylus breaks contact with the pen digitizer, the control program 282 enters state 287.

In state 287 the control program 282 assumes that the stylus will continue to be in the pen mode. Thus, local ink will follow the trajectory of the stylus while the top of the stylus remains in contact with the pen digitizer, or until a mode message is received from the host computer 101, whichever arrives earlier. Since the initial policy decision is a guess, the local inking is drawn using a single pixel-wide style and an XOR ("exclusive OR"') operation, in which the pixels along the trajectory of the stylus are inverted. While in state 287, the pen events associated with the trajectory of the stylus are accumulated in the pen event buffer 284.

If the mode message received in state 287 indicates that the stylus is in mouse mode, i.e. the policy decision was wrong, the control program 282 then enters a state 290, in which the accumulated pen events in pen event buffer 284 are used to erase the stylus stroke. Since the initial draw is accomplished by a bit XOR ("exclusive O.sup.R") operation at the appropriate positions of the frame buffer, erasure is simply provided by the same XOR operation at the same positions of the frame buffer. The control program 282 then enters state 286. However, if the mode message received in state 287 confirms that the stylus is in pen mode, the accumulated pen events of pen event buffer 284 are used to redraw on the LCD 113C, using the line style and color specified on the mode message.

Under a convention of the Pen Windows software, starting a stroke of the stylus with the barrel button depressed (for active stylus systems) indicates an erase ink operation in pen mode. The control program 282 recognizes this convention and refrains from inking during this stroke without waiting for confirmation from the host computer 101. In addition, the control program 282 does not change modes across an erasing stroke: i.e., if the stylus is in the pen mode prior to the erase stroke, the stylus remains in the pen mode after the erase stroke; conversely, if the stylus is in the mouse mode prior to the erase stroke, the stylus remains in the mouse mode after the erase stroke.

Since all the pen events used in local inking on the wireless interface device 100 are also processed in the host computer 101, the trajectory of local inking must coincide identically with the line drawn at the host computer 101. Because of local inking, processing by the host computer 101 within the human perceptual response time is rendered unnecessary. Thus, in the host computer 101, the pen events can be queued at pen event buffer 264, to be retrieved one at a time by pen event injector 274. Hence, when pen event buffer 264 is suitably sized, data loss due to overflow by RC buffer 275 is prevented.

Alternatively, the control program 282 can also be implemented to follow a "retractable ball-point pen" paradigm. Under this paradigm, the user controls a local stylus mode of the stylus, such that inking occurs when the stylus is set to be in the local pen mode, and no inking occurs when the stylus is in the local mouse mode. If the local stylus mode conforms with the mode expected by Pen Windows, the image seen on the LCD display of the video display subsystem 113 is the same as described above with respect to state 287 of the control program 282. If the local stylus mode is the mouse mode, and Pen Windows software expects stylus 110 to be in the pen mode, the subsequent video events from host computer 101 would provide the required inking. Finally, if the local stylus mode is the pen mode and Pen Windows software expects the stylus to be in the mouse mode, inking would be left on the screen of video display subsystem 113. Under this paradigm, the user would eliminate the erroneous inking by issuing a redraw command to Pen Windows.

One embodiment of the invention is illustrated in the schematic drawings, FIGS. 11-30. Referring to FIG. 11, the system may include a CPU 112, such as an AMD Model No. AM386DXLV microprocessor. The CPU 112 includes a 32-bit data bus D[0..31] as well as a 32-bit address bus A[2. .31]. Both the data bus D[0..31] as well as the address bus A[2..31] are connected to the processor bus 150 (FIG. 4), for example, an AT bus. As will be discussed in more detail below, the system controller 129 (FIG. 4) performs various functions including management of the processor bus 150. In order to conserve power, a 3volt microprocessor may be used for the CPU 112. As such, a 3volt supply 3V CPU is applied to the power supply VCC pins on the CPU 112. The 3volt supply 3V.sub.-- CPU is available from a DC-to-DC converter 300 (FIG. 26) by way of a ferrite bead inductor 302. In particular, the DC-to-DC converter 300 includes a 3volt output, 3V.sub.-- CORE. This output, 3V.sub.-- CORE, is applied to the ferrite bead inductor 302 and, in turn, to the power supply pins VCC of the CPU 112. In order to prevent noise and fluctuations in the power supply voltage from affecting the operation of the CPU 112, the power supply voltage 3V CPU is filtered by a plurality of bypass capacitors 304 through 330.

The 3volt supply 3V.sub.-- CPU is also used to disable unused inputs as well as to pull various control pins high for proper operation. For example, the 3volt power supply 3V.sub.-- CPU is applied to the active low N/A and BS16 pins of the CPU 112 by way of a pull-up resistor 332. In addition, the signals BE[0..3], W/R, D/C, M/IO and ADS are pulled up by a plurality of pull-up resistors 334 through 348.

The CPU 112 is adapted to operate at 25 megahertz (MHz) at 3.0 volts. A 25 MHz clock signal, identified as CPU CLK, available from a clock generator 398 (FIG. 13), is applied to a clock input CLK2 on the CPU 112 by way of a resistor 349 and a pair of capacitors 351 and 353. The AMD Model No. AMD386DXLV microprocessor supports a static state, which enables the clock to be halted and restarted at any time.

The wireless interface device 100 includes a speaker 355. The speaker 355 is under the control of the system controller 129 (FIG. 12). In particular, a speaker control signal SPKR from the system controller 129 is applied to a source terminal of a field-effect transistor (FET) 357 for direct control of the speaker 355. The drain terminal is connected to the speaker 355 by way of a current-limiting resistor 359 and a bypass capacitor 371. Normally, the speaker 355 is active all the time. In particular, the gate terminal of the FET 357 is connected to the system ground by way of a resistor 373. The gate terminal of the FET 357 is also under the control of a speaker disable signal SPKRDISABLE, available from the keyboard controller 125 (FIG. 15). The speaker disable signal SPKRDISABLE is active high. Thus, when the speaker disable signal SPKRDISABLE signal is low, the FET 357 is turned on to enable the speaker signal SPKR from the system controller 129 to control the speaker 355. When the speaker disable signal SPKRDISABLE is high, the FET 357 is turned off to disable the speaker 355.

Referring to FIG. 12, the system controller 129 is connected between the local processor or AT bus 150 and the system ISA bus 151. The system controller 129 performs a variety of functions including that of system controller, DRAM controller, power management, battery management and management of the local AT bus 150. The system controller 129, preferably a PicoPower Pine Evergreen 3, Model No. 86C368 system controller, is a 208-pin device that operates at 33 MHz with a full 5-volt input or a hybrid 5-volt/3.3-volt input. At 3.3 volts the system controller 129 is adapted to reliably operate at 20 Mhz and perhaps up to 25 Mhz.

The system controller 129 includes several system features including support of several clock speeds from 16 to 33 MHz. In addition, the system controller 129 includes two programmable non-cacheable regions and two programmable chip selects, used for universal asynchronous receiver transmitter (UART) interface 134 and the radio interface 114B as discussed below.

The system controller 129 supports both fast GATE A20 and a fast reset control of the CPU 112. In particular, the system controller 129 includes a 32-bit address bus A[0..31] that is connected to the local AT bus 150. The address line A[20] is used to develop a signal CPUA20, which is applied to the A20 pin on the CPU 112 and also applied to an AND gate 379 (FIG. 11) to support a port 92H for a fast GATE A20 signal. A fast reset signal RSTCPU is also generated by the system controller 129. The fast reset signal RSTCPU is applied to the reset pin RESET of the CPU 112 for fast reset control.

The system controller 129 also provides various other system level functions. For example, the system controller 129 includes a register at address 300H. By setting bit 12 of this register, a ROM chip select signal ROMCS is generated, which enables writes to the flash memory system 117 (FIG. 25), which will be discussed below. A keyboard controller chip select signal KBDCS for the keyboard controller 125 (FIG. 15), as well as general purpose chip select signals GPCS1 and GPCS2 for selecting between the RF controller 114A, the UART 134 (FIG. 16) or the pen controller 110A (FIG. 21), are generated by the system controller 129.

The system controller 129 is connected to the system ISA bus 151 by way of a 16-bit system data bus SD[0..15] and a 24-bit system address bus SA[0..23] of which only 8-bits SA[0..7] are used. The system controller 129 is also connected to the 32-bit local processor data bus D[0..31], as well as the local processor address bus A[0..31].

All of the ground pins GND on the system controller 129 are tied to the system ground. Both 3volt and 5-volt power supplies are applied to the system controller 129. In particular, a 5-volt supply 5V.sub.-- EG is applied to the power supply pins VDD of the system controller 129. The 5-volt supply 5V.sub.-- EG is available from DC-to-DC converter 300 (FIG. 26) by way of a ferrite bead inductor 381 (FIG. 12). More particularly, a 5-volt supply signal 5V.sub.-- CORE from the DC-to-DC converter is applied to the ferrite bead inductor 381, which, in turn, is used to generate the 5-volt supply signal 5V.sub.-- EG. In order to stabilize the 5-volt supply signal 5V.sub.-- EG, a plurality of bypass capacitors 1101-1111 (FIG. 13) are connected between the 5-volt supply 5V.sub.-- EG and system ground.

A 3volt power supply 3V.sub.-- EG is also applied to the system controller 129 and, in particular, to the power supply pins VDD/3V. This 3volt supply 3V.sub.-- EG is also obtained from the DC-to-DC converter 300 (FIG. 26) by way of a ferrite bead inductor 358. More particularly, 3volt supply 3V.sub.-- CORE, available at the DC-to-DC converter 300, is applied to the ferrite bead inductor 358, which, in turn, is used to generate the 3volt power supply signal 3V.sub.-- EG. A plurality of bypass capacitors 360, 362 and 364 are connected between the 3volt supply 3V.sub.-- EG and system ground for stabilizing.

The system controller 129 is reset by a reset signal RCRST (FIG. 20) on power up. The reset signal RCRST is developed by the 3volt power supply 3V.sub.-- EG, available from the DC-to-DC converter 300 (FIG. 26) and circuitry which includes a resistor 359, a capacitor 361 and a diode 363. Initially on power up, the capacitor 361 begins charging up from the 3volt supply 3V EG through the resistor 359. During this state, the diode 363 is non-conducting. As the capacitor charges, the level of the reset signal RCRST rises to reset the system controller 129. Should the system be turned off or the 3volt supply 3V.sub.-- EG be lost, the diode 363 provides a discharge path for the capacitor 361.

In order to assure proper operation of the system controller 129, a number of signals are pulled up to either five volts or three volts or pulled down by way of various pull-down resistors. More specifically, the signals IOCS16, MASTER, MEMCS16, REFRESH, ZWS, IOCHCK, GPI01/MDDIR and GPI02/MDEN are pulled up to the 5-volt supply 5V.sub.-- EG by way of a plurality of pull-up resistors 1113-1129, respectively. Similarly, the signals BUSY, FERR, LOCAL, SMIADS and RDY are pulled up by a plurality of pull-up resistors 1131 through 1139. In addition, the general purpose chip select signals GPCS1 and GPCS2 are pulled up to the 5-volt power supply signal 5V.sub.-- EG by way of a pair of pull-up resistors 375 and 377. Certain signals are pulled low by way of pull-down resistors in order to assure their operating state. In particular, the signals KBC-PO4, LB/EXTACT, RING, EXTACT/VLCLK and HRQ206 are pulled down by the pull-down resistors 388 to 396. The signal BLAST is tied directly to the system ground.

As mentioned above, the system controller 129 is capable of running at different clock frequencies, depending upon the voltage applied, while supplying a clock signal to the CPU 112. Even though the system controller 129 can supply either a 1X or a 2X clock signal to the CPU 112, the system controller 129 requires a 2X clock for proper operation. Thus, a 2X clock signal CLK2IN, available from a clock generator circuit 398 (FIG. 13), is applied to the clock 2X pin CLK2IN of the system controller 129. In addition, 32 kilohertz (KHz) and 14 megahertz (MHz) clock signals are also applied to the system controller 129, available from the clock generator circuit 398, for proper operation. The system controller 129, in turn, provides a CPU clock signal CPUCLK to the CPU 112 and in particular to its clock 2-pin CLK2 by way of a resistor 1141 and the capacitors 1143 and 1145.

The system controller 129 is adapted to be configured during an RC-RESET mode. In particular, the DRAM memory address lines MA[0..10], normally used for addressing the DRAM 111A (FIGS. 18 and 24), are pulled high or low in order to configure the system controller 129. More particularly, the DRAM memory address lines MA[0..10] are applied to either pull-up or pull-down resistors for configuration as illustrated in FIG. 17. Table 2 below illustrates the configuration shown.

As shown, the DRAM memory address lines MA[0 ..10] are shown with bits MA0, MA5 and MA7 pulled high to the 3-volt power supply voltage 3V.sub.-- EG by way of a plurality of pull-up resistors 400, 402 and 404. The remaining DRAM address line bits MA1, MA2, MA3, MA4, MA6, MA8, MA9 and MA10 are pulled low by a plurality of pull-down resistors 406 through 420, respectively. The DRAM memory address lines MA[0. .8] are also coupled to a plurality of coupling resistors 422 to 438 form a 9-bit DRAM address bus BMA[0..8].

The system controller 129 functions as a DRAM controller and is capable of supporting up to 64 megabytes of memory, divided among one of four banks and can support 256K, 512K, 1M, 2M and 4M of memory in any width. The system controller 129 includes a pair of registers associated with each bank of DRAM. The first register stores the total amount of DRAM connected to the system while the second identifies the starting address for each bank. Referring to FIGS. 18 and 24, two 1 Mbyte banks are connected to the DRAM memory address bus BMA[0..8] and to the processor data bus 150, D[0..31].

In order to conserve power, 3volt DRAM 111A is used. The 3volt power supply 3V-RAM is applied to the VCC terminals of each of the DRAMS 111A. The 3volt power supply 3V.sub.-- RAM is available from the DC-to-DC converter 300 (FIG. 26) by way of a ferrite bead inductor 440 (FIG. 18). In particular, a 3volt supply 3V-CORE available at the DC-to-DC converter 300 is applied to the ferrite bead inductor 440 to generate the 3volt DRAM supply 3V.sub.-- RAM. A plurality of bypass capacitors 425-439 (FIG. 18) are connected between the DRAM supply voltage 3V.sub.-- RAM and system ground.

The system controller 129 generates the appropriate row address strobes (RAS) and column address strobes for the DRAM 111A. In particular, the column address strobe lines CASO[0..3] are applied to the upper and lower column address strobe pins (UCAS and LCAS) on the DRAM 111A by way of a plurality of coupling resistors 442 to 450 (FIG. 12). Similarly, the row address signals RAS0 and RAS1 are applied to the row address strobe pins on the DRAM 111A by way of a plurality of coupling resistors 448 and 450. Writing to the DRAMS 111A is under the control of a DRAM write enable signal BRAMW, applied to the write enable pin WE on the DRAM 111A. The DRAM write enable signal BRAMW is generated by the system controller 129 by way of a coupling resistor 452.

An EEPROM or NVRAM 111B (FIG. 12) may be used to maintain system configuration parameters when the system is powered off. All user changeable parameters are stored in the EEPROM 111B. For example, pen calibration data and passwords, used during boot up, may be used in the EEPROM 452. The contents of the EEPROM 111B may be shadowed into a CMOS memory when the system is active. Communication with the EEPROM 111B is under the control of the system controller 129 and in particular, a pair of programmable input/output pins GPIO1 and GPI02. The GPIO1 provides a clock signal to the EEPROM 111B while the pin GPI02 is used for data transfer.

As discussed above, the wireless interface device 100 also includes the flash memory 117 (FIG. 25), which is used for storing the BIOS. The system controller 129 allows for direct shadowing of the BIOS by enabling the appropriate address space to read the FLASH/DRAM write mode which allows all reads to come from the flash device with writes to the DRAM 111A memory devices.

A main memory map as well as an I/O memory map are provided in Tables 3 and 4.

In addition to system control features and DRAM control, the system controller 129 provides various other functions. The power management function and NVRAM controller have been discussed above. The system controller 129 also controls all operations on the local AT bus 150. The AT bus clock is derived from the clock CLK2IN pin that is divided to achieve an 8 MHz bus rate.

The system controller 129 also includes a number of programmable pins which enhance its flexibility. For example, four general purpose input/output pins GPIO[0..3] are provided; each of which may be independently set for input or output. The GPIO1 and GPIO2 pins are used for the EEPROM 111B as discussed above. The GPIO0 pin and GPIO3 pin may be used for various purposes. In addition to the programmable input/output pins, the system controller 129 includes two general purpose chip select pins GPCS1 and GPCS2 as well as a plurality of programmable output pins PC[0..9]. The programmable chip selects GPCS1 and GPCS2 are used for the pen controller 110A, UART 134 and the radio interface 114B.

Peripheral devices connected to the system ISA bus 151 are controlled by an integrated peripheral controller 128 as discussed above. The integrated peripheral controller 128 may be a PicoPower Model No. PT82C206F which can be operated at either 3.3 or 5 volts. As will be discussed in more detail below, the integrated peripheral controller 128 includes several subsystems such as: DMA Control; Interrupt Control; Timer Counter; RTC Controller; CMOS RAM and Memory Mapper.

The IPC 128 includes two type 8259A compatible interrupt controllers which provide 16 channels of interrupt levels, one of which is used for cascading. The interrupt controller processes all incoming interrupts in order as set forth in Table 5.

The integrated peripheral controller (IPC) 128 (FIG. 14) is connected to the system data bus SD[0. .15]. Addressing of the IPC 128 is accomplished by two bits SA0 and SA1 from the system address bus SA[0..23] and eight bits A[2..9] from the local address bus A[0..31]. The address bits from the local address bus A[2..8] are converted to 5 volts by way of a 3- to 5-volt signal converter 453 (FIG. 14) to develop the 5-volt address signals XA[2..8]. A 32-kilohertz clock signal 32-KHz from the clock generator 398 (FIG. 13) is applied to the clock input OSC1 of the IPC 128.

Referring to FIG. 20, in order to prevent spurious operation of the IPC 128 before the system power supply is stabilized, a power good signal PWRGOOD is applied to a power good pin PWRGD. The power good signal PWRGOOD is a delayed signal which assures that the 5-volt power supply has stabilized before the IPC 128 is activated. In particular, a 5-volt power supply 5V.sub.-- CORE is applied to a delay circuit which includes a resistor 454, a diode 456 and a capacitor 458. Initially, the 5-volt power supply signal 5V.sub.-- CORE is dropped across the resistor 454. While the capacitor 458 is charging, the diode 456 is in a non-conducting state. As the capacitor 458 begins to charge, the voltage at the anode of the diode 456 increases as a function of the RC time constant. When the capacitor 458 is fully charged, it approaches the value of the power supply voltage 5V.sub.-- CORE. When the capacitor 458 becomes fully charged, the power good signal PWRGOOD is applied to a power good pin PWRGD at the IPC 128 for enabling the IPC 128 after the power supply has stabilized. The diode 456 provides a discharge path for the capacitor 458 when the power supply is shut off. The power good signal PWRGOOD is also used to reset the keyboard controller 125.

A 5-volt power supply 5V.sub.-- CORE from the DC-to-DC converter 300 (FIG. 26) is applied to a ferrite bead inductor 460 (FIG. 13) to develop a 5-volt power supply 5V.sub.-- 206, which, in turn, is applied to the power supply pins VCC of the IPC 128. In order to delay application of the 5-volt power supply 5V.sub.-- 206 as discussed below, a charging circuit which includes a serially coupled resistor 462 and a capacitor 464 are connected between the power supply voltage 5V.sub.-- 206 and the system ground. A power supply reset signal PSRSTB, an active low signal, is applied to the junction between the resistor 462 and the capacitor 464 to discharge the capacitor 464 when the power supply is reset. Moreover, in order to stabilize the voltage of the power supply 5V.sub.-- 206, a plurality of bypass capacitors 466 and 468 are connected between the power supply 5V.sub.-- 206 and system ground.

In order to assure proper operation of the circuit, various pins of the IPC 128 are pulled low while various other pins are pulled high. In particular, the input/output read and write signals IOR and IOW are pulled up to the power supply voltage 5V.sub.-- 206 by a pair of pull-up resistors 470 and 472. In addition, the interrupt request pin IRQ10 is pulled up to the power supply voltage 5V.sub.-- CORE by a pull-up resistor 474. The signals OUT2, REFREQ, AEN16 and AEN8 are pulled low by pull-down resistors 455-461 while the signal TEST.sub.-- MODE2 is pulled up to the supply voltage 5V.sub.-- CORE by a pull-up resistor 463.

Even though the IPC 128 includes a direct memory access (DMA) controller, this function is not required by the system. As such, the direct memory access request pins DREQ[0..7] are pulled low by a pull-down resistor 476 to system ground. In addition, as set forth in Table 5 above, various interrupt levels are unused. For example, as shown in Table 5, interrupt levels IRQ3, IRQ6, IRQ7, IRQ9, IRQ11, IRQ12, IRQ14, and IRQ15 are not used. Thus, these interrupt levels are pulled low by a pull-down resistor 478.

As illustrated in Table 5, interrupt levels IRQ4 and IRQ5 are used for the COM1 and pen controller interrupt levels, IRQ4 and IRQ5. To assure that these levels are proper, the IRQ4 and IRQ5, which are active high, are pulled low by pull-down resistors 480 and 482.

Interrupts by the system controller 129 and IPC 128 INTR.sub.-- EG and INTR206 are applied to the CPU 112 by way of a diode 479 and pull-up resistor 481 (FIG. 14). In particular, the interrupt signals INTR.sub.-- EG and INTR206 from the system controller 129 and IPC 128, respectively, are applied to the cathode of the diode 479 while the anode is pulled up to the power supply voltage 3V.sub.-- CORE by the pull-up resistor 481. The logic level of the anode is set by the interrupt signal INTR, which is applied to the CPU 112. When the interrupt signals INTR206 and INTR.sub.-- EG are high, the diode 479 does not conduct and the CPU 112 interrupt signal INTR will be high. When either of the interrupt signals INTR.sub.-- EG or INTR206 are low, the diode 479 conducts, forcing the CPU 112 interrupt signal INTR low.

The IPC 128 also includes a type 8254 compatible counter/timer which, in turn, contains three 16-bit counters that can be programmed to count in either binary or binary-coded decimal. The zero counter output is tied internally to the highest interrupt request level IRQ0 so that the CPU 112 is interrupted at regular intervals. The outputs of the timers 1 and 2 are available for external connection. In particular, internal timer 1 generates one signal, OUT1, which is used to generate a DRAM refresh request signal REFREQ to the CPU 112. The internal timer 2 generates an output signal OUT2 that is used to generate speaker timing. All three internal timers are clocked from a timer clock input TMRCLK at 1.2 megahertz from the system controller 129.

As mentioned above, the IPC 128 includes a real time clock (RTC) controller which maintains the real time. The real operational time is maintained in a CMOS RAM that can be accessed through registers 70H and 71H. The memory map for the CMOS memory is provided in Table 6 as shown below:

The area designated as User RAM is used by the system BIOS to save the status of the system configuration registers. The alarm bytes may be used to set and generate an interrupt at a specific time. When periodic interrupt is required, the two most significant bits in the alarm register can be set high.

The various clock signals used for the system are provided by the clock generator circuit 398 (FIG. 13). The clock circuit 398 includes a clock generator, for example, an Integrated Circuit Designs Model No. ICD2028. A 14.318 MHz crystal 484 and a 32.768 KHz crystal 486 are applied to the clock generator 488. In particular, the crystal 484 is applied to a pair of X1 and X2 input pins along with a plurality of capacitors 489, 490, 492 and an input resistor 494. Similarly, the crystal 486 is applied to input pins XSYSB1 and XSYSB2. A pair of capacitors 496 and 498 are connected across the crystal 486.

The clock generator IC 488 provides three clock outputs CLKA, CLKB and CLKD. The clock A output CLKA is used to develop an 8-MHz clock signal for the keyboard controller 125 by way of a resistor 500 and capacitors 502 and 504. The clock B output CLKB is used to develop a clock 2X output signal CLK2IN for the system controller 129 by way the resistors 506, 508 and 510 and a pair of capacitors 512 and 514. The clock D output signal CLKD is used to generate a 1.84 MHz signal for use by the Universal Asynchronous Receiver Transmitter (UART) 134 by way of a resistor 516 and capacitors 518 and 520. As mentioned above, the system controller 129 also requires a 14 MHz clock signal. This clock signal is developed by way of a system bus output pin SYSBUS, a resistor 522 and a pair of capacitors 524 and 526.

Selection of the various clock output signals is available by way of the select pins S0, S1 and S2. These pins S0, S1 and S2 are pulled up to the 3volt power supply 3V.sub.-- CORE by way of pull-up resistors 521, 523 and 525. The 3volt power supply signal 3V.sub.-- CORE is available from the DC-DC converter 300 (FIG. 26).

The clock generator 488 utilizes a 3volt power supply CLOCK.sub.-- VCC (FIG. 13). The 3volt power supply CLOCK.sub.-- VCC is available from the DC-to-DC converter 300 (FIG. 26) by way of an in-line ferrite bead inductor 530. In particular, the 3volt power supply 3V.sub.-- CORE is applied to the ferrite bead inductor 530 to generate the power supply for the CLOCK.sub.-- VCC for the clock generator 488. This power supply CLOCK.sub.-- VCC is applied to the power supply pin VDD. The power supply signal CLOCK.sub.-- VCC is also used as analog supply AVDD to the clock generator IC 488 and is applied to the analog supply AVDD by way of the resistor 532 and a pair of capacitors 534 and 536. The power supply signal CLOCK.sub.-- VCC is also applied to the battery pin VBATT of the clock generator IC 488 by way of a diode 537 to prevent any back feeding.

A number of the circuits in the system operate at either 3.3 volts or 5 volts. Thus, a plurality of bi-directional signal level translators 542 and 544 (FIG. 14) are provided, as well as the translator 453 previously discussed. The signal level translators 453, 542 and 544 may be as supplied by Integrated Circuit Technology, Model No. FCT164245T. Each of the signal level translators 453, 542 and 544 includes a 3volt supply 3V.sub.-- CORE and a 5-volt supply 5V.sub.-- CORE, available from the DC-to-DC converter 300 (FIG. 26). In order to stabilize the voltage of the 3- and 5-volt power supplies, 3V.sub.-- CORE and 5V.sub.-- CORE, a plurality of bypass capacitors are utilized. In particular, the bypass capacitors 546 through 552 are connected between the 3volt supply 3V.sub.-- CORE and system ground. Similarly, the bypass capacitors 554 through 560 are connected between the 5-volt supply 5V.sub.-- CORE and system ground. The ground terminals of each of the signal level translators 542, 544 and 453 are also tied to system ground.

Each of the signal level translators 542, 544 and 453 includes two 8-bit programmable input/output pins. More particularly, the first 8-bit group 1A/1B[1..8] is under the control of an operate/enable pin 1OE, which is active low, while the second bank 2A/2B[1..8] is under the control of an output/enable pin 2OE, also active low. The direction of the input pins and output pins (i.e., A relative to B) is under the control of direction pins 1DIR and 2DIR. The direction pin 1DIR controls the direction of the pins 1A/1B[1..8], while the pin 2DIR controls the direction of the pins 2A/2B[1..8].

The signal level translator 453 is used to convert the local data bus bits D[16..31] and the system data bus bits SD[0..15]. Both the local data bus D[16..31] as well as the system data bus SD[0..15] are bi-directional. In this application the processor bus 150 data bits D[31...16] are being mapped to the system data bus bits SD[15...0].

The direction of the signal level translator 542 is under the control of a signal direction signal SDIR, available at the system controller 129. The signal direction signal SDIR is applied to both the direction control pins 1DIR and 2DIR of the signal level translator 542. The operate/enable inputs 1OE and 2OE are under the control of system data enable inputs signals, SDEN3 and SDEN2, respectively; also under the control of the system controller 129.

The signal level translator 544 is used to map the signal levels of the local address bus bits A[23...8] to the system address bus bits SA[23...8]. More particularly, the local address bits A[23..16] are applied to pins 1A[1..8] while the local address bits A[15..8] are applied to the pins 2A[1..8]. Similarly, the system address bits SA[23..16] are connected to the pins 1B[1..], while the system address bits SA[15..8] are applied to the pins 2B[1..8]. In this case, the operate/enable pins 1OE and 2OE, both active low, are connected to system ground in order to permanently enable the signal level translator 544. The direction control pins 1DIR and 2DIR are permanently set such that the data always flows from A to B. In particular, the directional pins 1DIR and 2DIR are connected to the 3volt power supply 3V.sub.-- CORE by way of a pull-up resistor 562.

The signal level translator 542 is used to convert the signal levels of the 3volt clock output signals 14 Mhz, 1.84 Mhz, 32 Khz and 8 Mhz to 5-volt levels, as well as to convert the 3volt local address bits A[2..8] to 5-volt address bits XA[2..8] for use by the IPC 128, as discussed above. More particularly, the system address bits, A[2..8] are applied to the pins 1A[1..8]. The clock signals 14 MHz, 1.84 MHz, 32 KHz and 8 MHz are applied to the pins 2A1, 2A3, 2A6 and 2A8, respectively, to produce corresponding 5-volt level signals 14 MHz.sub.-- 5V, 1.84 MHz.sub.-- 5V, 32 KHZ.sub.-- 5V and 8 MHz.sub.-- 5V signals at pins 2B1, 2B3, 2B6 and 2B8, respectively. The unused pins 1A8 and 2B8 are pulled low by way of pull-down resistors 564 and 565, respectively. The operate/enable pins 1OE and 2OE are tied to system ground to permanently enable the signal level translator 542. The directional pins 1DIR and 2DIR are pulled up to the 3volt power supply voltage 3V.sub.-- CORE by way of a pull-up resistor 566 to permanently force the direction from A to B.

Referring to FIG. 15, the system includes a keyboard controller 125, which performs several functions, including battery monitoring, LCD status control, brightness and contrast control, as well as keyboard control. In addition, the system also maintains the status of the remaining battery life, and also provides information to the system controller 129 when the battery voltage is low or other critical battery condition has occurred. In operation, the keyboard controller 125 will maintain the current status of the battery level until data is requested. When a critical battery condition event occurs, the keyboard controller 125 generates an SMI interrupt. As discussed above, the intelligent battery pack (IBP) 130 provides an indication of the percentage of remaining battery capacity. Communication between the IBP 130 and the keyboard controller 125 is by way of a bi-directional serial data bus, which includes a clock line BATCLK and a data line BATDATA. The data line BATDATA is a bi-directional line, which allows for bi-directional communication with the IBP 130. The clock line BATCLK is driven by the IBP 130, but may be pulled low by the keyboard controller 125.

The bi-directional serial data bus is connected to the port pins P4.2 and P4.3 on the keyboard controller 125. In particular, the port pin P4.2 is used for the serial battery data BATTDATA. An NPN transistor 570 is connected to the port pin P4.2 to disconnect the keyboard controller 125 from the IBP 130 during power down. In particular, the collector terminal of the NPN transistor 570 is connected to the port pin P4.2, while the emitter terminal forms a battery data signal BATTDATA. The base of the NPN transistor 570 is biased on by way of a biasing resistor 572 that is connected to a 5-volt power supply 5V.sub.-- KBD. The collector is pulled high by way of a pull-up resistor 574 connected to the 5-volt power supply 5V.sub.-- KBD.

Similarly, the battery clock signal BATTCLK is connected to the port 4.3 on the keyboard controller 125 by way of an NPN transistor 576. The collector terminal of the NPN transistor 576 is connected to the port 4.3 as well as to a pull-up resistor 578 and the 5-volt power supply 5V.sub.-- KBD. The NPN transistor 576 is turned on anytime the power supply to the keyboard 5V.sub.-- KBD is powered up by way of a biasing resistor 580. The emitter of the NPN transistor 576 forms the battery clock signal BATTCLK.

In addition to battery management, the keyboard controller 125 also supports an external PS/2-type keyboard, as well as a PS/2-type bar code reader, connected to a keyboard connector 140 (FIG. 29). Communication between the keyboard or bar code reader (not shown) is by way of a standard type PS-2 two-wire bus connected to serial ports P4.6 and P4.7. In particular, the keyboard data KDATA is pulled up to the 5-volt voltage supply 5V.sub.-- CORE by way of a pull-up resistor 582 while the keyboard clock signal KCLK is pulled up the 5-volt supply 5V.sub.-- CORE by way of a pull-up resistor 584.

Referring to FIG. 29, the keyboard connector 140 may be a 6-pin MINI-DIN connector or a DB-8 connector as shown. Pins 6-9 are connected to system ground. Pin 4 of the connector 140 is pulled up to the power supply voltage 5V.sub.-- CORE by way of a fuse 579 and is filtered by a capacitor 581 and an inductor 583. The data signal KDATA is applied to pin 1 by way of a current-limiting resistor 585, while the clock signal KCLK is applied to pin 5 by way of a current-limiting resistor 587 and a pair of capacitors 589 and 591. These clock and data signals KCLK and KDATA are connected to the ports P4.6 and P4.7, respectively, for serial communication with an external keyboard or bar code reader.

Additionally, the keyboard controller 125 may be used to control the brightness level as well as the contrast level of the LCD display. More particularly, referring to FIG. 27, a contrast signal CONTRAST, available at port 0, pin 1 of the keyboard controller 125 (FIG. 15) is used to adjust the contrast level of the LCD display. The contrast signal CONTRAST is applied to an adjustment terminal ADJ of a negative 24-volt DC voltage supply, which can be incrementally adjusted in steps by a 24-volt DC supply 586 (FIG. 27), for example, a Maxim Model No. 749, which provides for 64-step adjustment. Thus, each high pulse will increment the contrast of the LCD display by one step. With a 64-step device, sixty-three pulses rolls the counter over and decreases the contrast by 1. The 24-volt DC supply 586 is under the control of an enable signal ENAVEE, available from the video controller 113A (FIG. 19).

In order to assure proper operation, the 24-volt supply 586 is connected in a circuit as shown in FIG. 27, which includes a plurality of capacitors 588, 590, 592, 594; a plurality of resistors 596, 598, 600 an inductor 602; a PNP transistor 604; and a zener diode 606. The output of the circuitry is a nominal negative 24-volt signal LCDVEE, which is adjustable in 64 increments by way of the CONTRAST signal, as discussed above, to vary the contrast level of the LCD display.

The keyboard controller 125 also controls the brightness of the LCD display. In particular, brightness adjustment signals BRIGHTNESS.sub.-- UP, BRIGHTNESS.sub.-- DOWN (FIG. 15) are available at port 1, pins 6 and 7. These signals BRIGHTNESS.sub.-- UP and BRIGHTNESS.sub.-- DOWN are normally pulled up to the 5-volt supply 5V.sub.-- KBD by way of a pair of pull-up resistors 608 and 610. These signals BRIGHTNESS.sub.-- UP and BRIGHTNESS.sub.-- DOWN are applied to a digital output potentiometer 612 (FIG. 27), for example a Dallas Semiconductor Model No. DS1669-50. The digital output potentiometer 612 is powered by a 5-volt power supply 5V.sub.-- CORE, which is also used to pull up an unused output terminal, RH.

The brightness control signals BRIGHTNESS.sub.-- UP and BRIGHTNESS.sub.-- DOWN are applied to the increment and decrement terminals, UC and DC of the digital output potentiometer 612. The output of the digital output potentiometer 612 is a variable resistance signal, which forms the brightness control signal BRIGHTNESS. This brightness control signal BRIGHTNESS is pulled down by a pull-down resistor 614.

The brightness control signal BRIGHTNESS from the digital output potentiometer 612, as well as a backlight control signal BACKLITEON and a backlight power signal BACKLITEPOWER are connected to the system by way of a 6-pin connector 615 (FIG. 27). The backlight control signal BACKLITEON is connected to pin 4 of the connector 615 and pulled low by way of a pull-down resistor 617. The power control signal BACKLITEPOWER is applied to pins 1 and 2 while the backlight brightness control signal BRIGHTNESS is applied to pin 3. The backlight control signal BACKLITEON is available from the video controller 113A (FIG. 19) and is used to power the backlight on the LCD. The backlight power signal BACKLITEPOWER, available from an FET 619 (FIG. 20), is under the control of the backlight power control signal BACKLITEON, available from the video controller 113A (FIG. 19).

The FET 619 (FIG. 20) is used to control power to both the LCD as well as the backlight. In particular, referring to FIG. 20, the backlight power control BACKLITEON, is used to control an NPN transistor 617 by way of a current-limiting resistor 621. The NPN transistor 621, in turn, is used to control the FET 619 to generate the backlight power signal BACKLITEPOWER at the drain terminal D1. The main power signal POWER (FIG. 28) is connected to the collector of the NPN transistor 617 by way of a resistor 623. The main power signal POWER is also applied to a source terminal 51 of the FET 615. A gate terminal G1 of the FET 615 is connected between the resistor 623 and the collector of the NPN transistor 625. The backlight power control signal BACKLITEON is used to conserve power under certain power management conditions discussed above. This signal BACKLITEON controls the NPN transistor 625. In particular, in a normal state, the backlight power control signal BACKLITEON is high, which turns ON the NPN transistor 625. When the NPN transistor 625 is ON, the gate terminal Gi of the FET 619 is connected to system ground, which turns the FET 619 ON, thereby connecting the main power signal POWER to the drain terminal D1 of the FET 619 to provide a power signal BACKLITEIN, which is filtered by a ferrite bead inductor 625 (FIG. 28) to provide the backlight power signal BACKLITEPOWER, that is applied to the LCD by way of the connector 615 (FIG. 27). When the backlight power control signal is low, for example, during a power management mode, the NPN transistor 625 turns OFF, thereby connecting the gate G1 of the FET 619 to the main power signal POWER by way of the resistor 623, thereby turning the FET 619 OFF, disconnecting power to the LCD.

The FET 619 may be supplied as a dual element with two FETs in a single package. As shown in FIG. 20, the gate G2, source S2 and drain D2 terminals of the FET 619 are used to control power to the LCD, under the control of an LCD enable signal ENAVDD, available from the video controller 113A (FIG. 19). In particular, the LCD enable signal ENAVDD is normally high and is de-asserted to disable the LCD power supply LCD.sub.-- POWER. This LCD enable signal ENAVDD is pulled low by a pull-down resistor 627 and applied to an inverter 629, whose output is connected to the gate terminal G2 of the FET 619. The LCD power supply signal LCD.sub.-- VCC (FIG. 19) is applied to the source terminal S2 of the FET 619, while the drain terminal D2 represents the LCD power signal LCD.sub.-- POWER, filtered by an inductor 629 and a capacitor 631. The LCD power signal LCD.sub.-- POWER is connected to the LCD by way of the connectors 732 or 734 (FIG. 22). In operation, the LCD power enable signal ENAVDD is high, which turns on the FET 619 to enable the LCD power supply LCD.sub.-- POWER. When the LCD power enable signal ENAVDD is de-asserted, the FET 619 is turned OFF.

The keyboard controller 125 (FIG. 15) is connected to the system data bus SD[0. .7]. The system address bit SA2 is used for addressing the keyboard controller 125. In particular, the address terminal of the keyboard controller 125 is connected to bit SA2 of the system address bus SA[0..23].

Power to the keyboard controller 125 is provided by way of a 5-volt supply 5V.sub.-- KBD, supplied to the power supply terminal VCC. The 5-volt supply 5V.sub.-- KBD, provided by the DC-to-DC converter 300 (FIG. 26) by way of an in-line ferrite bead inductor 618. In addition to supplying power to the keyboard controller 125, the 5-volt supply 5V.sub.-- KBD is used to pull-up various pins by way of pull-up resistors 620, 622, 624, 626, 628, 630, 632 and 634. In order to stabilize the 5-volt power supply 5V.sub.-- KBD, a plurality of bypass capacitors 636 and 638 are connected between the power supply 5V.sub.-- KBD and system ground.

As mentioned above, the keyboard controller 125 has various functions. One of those functions is to monitor when AC power is plugged into the machine from an AC adapter plug 633 (FIG. 29), connected to the external power supply signal AC/DCIN by way of a pair of EM1 filters 641 and 643, and a connector 645. In particular, an AC power signal ACPWR, available from an FET 635 (FIG. 20), is applied to port 3, pin 1 (FIG. 15) by way of an inverter 636. The external power supply signal AC/DCIN, available from the AC plug 633, is used to control the gate terminal of the FET 635, normally pulled down a pull-down resistor 637. A 5-volt supply 5V.sub.-- CORE is connected to the drain terminal while the source terminal is used for the AC power signal ACPWR, pulled down by a pull-down resistor 639. When an external power source is not connected to the FET 635, the signal ACPWR will be low. Once external power is connected to the connector 633, the signal AC/DCIN from the IBP 130 goes low, which, in turn, turns on the FET 635 to cause the signal ACPWR to go high.

The keyboard controller 125 also monitors the status of the radio. As such, an output from the radio TX/RX.sub.-- LED pin is applied to pin 2 of port 3 of the keyboard controller 125 by way of an inverter 638. When pin 1 of port 3 is high, the keyboard controller 125 interprets that the radio is in a transmit mode. Another signal from the radio CD.sub.-- LED is used to provide an indication to the keyboard controller 125 that that radio is in a receive mode. This signal CD.sub.-- LED is applied to pin 2 of port 3.

An 8 MHz clock signal 8 MHz.sub.-- 5V is used to drive the keyboard controller 125. The clock signal 8 MHz.sub.-- 5V is developed by the clock generator 398 and converted to a 5-volt level by way of the translator signal level translator 452.

The video controller 113A (FIG. 19) controls the video functions. The video controller 113A, for example, a model number CL-GD 6205 from Cirrus Logic, can support various video modes including a mono STN and a color TFT panel with up to 640.times.480 with 64 shades of gray. In addition, the video controller 113A will support 1024 by 768 resolution with 16 colors on a CRT through the aid of its on-board digital to analog converter.

The video controller 113A utilizes two clock sources for timing, generated by an internal clock generator to produce the required frequencies for the display and memory timing. Two separate analog power supply sources AVCCMCLK and AVCCVCLK are provided to the analog power supply inputs AVCC1VCLK and AVCC4MCOK on the video controller 113A. These analog power supply sources AVCCMCLK and AVCCVCLK are derived from the 3volt power supply 3V.sub.-- CORE, available at the DC-to-DC converter 300 (FIG. 26). In particular, the 3volt power supply 3V.sub.-- CORE is used to develop a 3volt power supply VGA.sub.-- VCC by way of an in-line ferrite bead inductor 642. The power supply VGA.sub.-- VCC, in turn, is filtered by a plurality of bypass capacitors 644-642, connected between the power supply VGA.sub.-- VCC and system ground. The 3volt power supply VGA.sub.-- VCC is used to develop the analog power supplies AVCCMCLK and AVCCVCLK by way of a plurality of resistors 654 and 656 as well as a plurality of by pass capacitors 658 to 664, connected to an analog ground AGND. The analog ground AGND is tied to the digital ground GND by way of a ferrite bead conductor 664.

The keyboard controller 125 also provides various miscellaneous system functions by way of its I/O ports 0, 1, and 3. Five port bits P0.0-P0.5 of port 0 are used for system control. Bit 0 is used to generate a signal KBC-P00, an active high signal, which disables the general purpose chip select signals GPCS1 and GPCS2, available at the system controller 129 (FIG. 12) during boot-up, until the signals GPCS1 and GPCS2 are properly configured. As discussed above, the general purpose chip select signals GPCS1 and GPCS2 are used for selecting the pen controller 110A (FIG. 21), the radio interface 114B (FIG. 16) and the UART (134). Bit PO.1 is used to generate a contrast signal CONTRAST, normally pulled low down by a pull-down resistor 639 (FIG. 5) for contrast control of the LCD as discussed above. Briefly, the contrast signal CONTRAST is used to step the 24-volt supply 586 (FIG. 27). Bit PO.2 is used to generate a keyboard shutdown signal KBSHUTDOWN. This signal KBSHUTDOWN, discussed below, is active low, and in conjunction a pen shutdown signal PEN.sub.-- SHUTDOWN, available at the pen controller 110A (FIG. 21), is used to generate a shutdown signal SHUTDOWN to shutdown the AC-to-DC converter 300 (FIG. 26) during low power conditions. More particularly, the keyboard shutdown signal KBSHUTDOWN, pulled up by a pull-up resistor 641, and the pen shutdown signal PEN.sub.-- SHUTDOWN, pulled low by a pull-down resistor 643, are diode ORed by a pair of diodes 645 and 647. The cathodes of the diodes 645 and 647 are joined to form the active low shutdown signal SHUTDOWN. If the keyboard shutdown signal KBSHUTDOWN is asserted, the shutdown signal SHUTDOWN will be forced low, which, in turn, is used to disable the DC-to-DC converter 300 (FIG. 26). Bit P0.3 is used to generate a signal FLASHVPP to enable the flash memory devices 742-748 (FIG. 25) to be programmed. In particular, when the signal FLASHVPP is low, the flash memory devices 742-748 can be programmed. Bit P0.4 is used to generate a signal KBC.sub.-- P04. The signal KBC.sub.-- P04 is an active high signal and is used to indicate to the system controller 129 (FIG. 12) that a low battery condition has occurred. Bit P0.5 is used for speaker control as discussed above. The pen P0.5 is used to generate the speaker disable signal SPKRDISABLE, an active high signal.

Port 1, bits P1.1, P1.5, P1.6, and P1.7 of the keyboard controller 125 are used for system functions. Bit P1.1 is configured as an input and is used to indicate to the keyboard controller 125 that the system is in a test mode. As discussed above, the test mode signal TEST-MODE is used to enable the flash memory device 742 (FIG. 25) to be programmed. In particular, as discussed above, the test mode signal TEST.sub.-- MODE is used to generate a decode signal FLIP.sub.-- SA18 (FIG. 17) for decoding of the flash memory device 742. Port 1, bits P1.5, P1.6, and P1.7 are used for LCD control. In particular, the pen P1.5 may be used for LCD status control the pens P1.6 and P1.7 are used for brightness control of the LCD as discussed above.

Port 3, bits P3.1, P3.2, P3.3, P3.4, P3.5, and P3.7 are configured as inputs. As discussed above, a signal ACPWR, available from the source of the FET 635 (FIG. 20), is applied to the pin P3.1. This signal ACPWR notifies the keyboard controller 125 that an external power source is connected to the system. The signal CD.sub.-- LED is applied to the pin P3.2. This signal, CD.sub.-- LED, available from the radio interface (FIG. 16), indicates that the radio is receiving a signal. A signal TX/RX.sub.-- LED, also available from the radio interface, is applied to the pin P3.3. This signal TX/RX.sub.-- LED indicates that the radio is in a transmit mode. A signal DOCKACK/: may be applied to the pin P3.4. This signal may be used to indicate to the keyboard controller 125 that a device is docked to the UART 134. The development of the signal DOCKACK/: does not form a part of the present invention. A second test mode signal TEST MODE.sub.-- 2 may be applied to the pin P3.5 for added functions. A signal PC5.sub.-- P37 is applied to the pen P3.7. This signal PC5.sub.-- P37 is available from the system controller 129 (FIG. 12) and indicates that the system is in a sleep state as discussed above.

The video controller 113A is connected to the system database SD[0. .15] as well as the system address bus SA[0..23] and is adapted to support the video memory 113B of either 256K by 16-bit or 256K by 4-bit video memory chips 666 or 668. These video memory chips 666 and 668, for example 256K by 16 dram memory chips, as manufactured by Toshiba Model No. NE4244170-70, are connected to a 16-bit video memory databus VMDATA[0..15] and the 9-bit video memory address bus VMADR[0..8]. The video memory chips 666 and 668 are accessed in the range from A000H-BFFFFH and are switched to allow access to a full 512 kilobyte range. The video memory chips 666 and 668 are provided with dual column address strobe (CAS) pins to allow byte selection. The video memory column address strobes LCAS and UCAS are under the control of the high and low video memory column address strobe low and high signals, VMCASL and VMCASH, which are applied to the LCAS and UCAS pins by way of a pair of current-limiting resistors 670 and 672 to generate the buffered CAS the lower and high CAS signals VMCISLBUF and VMCASHBUF. The row address strobe signal VMRAS from the video controller 113A, as well as the write/enable signal VMKE, are also applied to the video memory 666 and 668 by way of current limiting resistors 674 and 676 respectively. The output/enable pin on the video memory chips 666 and 668 is under the control of a video memory operate/enable signal VMOE. This video memory operate enable signal VMOE is generated by the video controller 113 and is applied directly to the video memory chip 666 and 668.

Various power supply signals VGA.sub.-- VCC, LCD.sub.-- VCC, VGABUS.sub.-- VCC and VMEM.sub.-- VCC are applied to the video controller 113A. The power supply VMEM.sub.-- VCC is applied to the VMEM.sub.-- VCC pins on the video controller 113A and is also used as the power supply for the video memory chips 666 and 668. The video memory power supply VMEM.sub.-- VCC may be supplied as either a 3volt or 5-volt power supply. More particularly, both a 3volt and 5-volt power supply 3V.sub.-- CORE and 5V.sub.-- CORE. Depending on whether 3volt or 5-volt operation is selected, only one of the component positions illustrated as ferrite bead inductors 680 or 682 will be populated to produce the power supply VMEM.sub.-- VCC.

As will be discussed in more detail below, the system also includes an LCD controller to control the LCD screen 113C. The power supply for the LCD controller LCD.sub.-- VCC can likewise be supplied as either three volt or five volt by way of the 3- and 5-volt power supply voltages 3V.sub.-- CORE and 5V.sub.-- CORE, available at the DC-to-DC converter 320 (FIG. 26). Depending on the voltage selected, only one of the component locations 684 and 686 will be populated to provide the LCD power supply voltage LCD.sub.-- VCC. In addition, a power supply voltage VGABUS.sub.-- VCC is used for the VGA bus. This power supply voltage VGABUS.sub.-- VCC is generated by the DC-to-DC converter 320 by way of a ferrite bead inductor 688.

In order to filter noise out of the power supply signals, various bypass capacitors are connected between the power supply signals and system ground. For example, a plurality bypass capacitors 690-696 are coupled between the power supply signal VMEM.sub.-- VCC and the system ground. Similarly, a pair of bypass capacitors 698 and 700 are connected between the power supply signal LCD.sub.-- VCC and the system ground. Lastly, a plurality of bypass capacitors 702 to 706 is connected between the power supply signal VGABUS.sub.-- VCC and the system ground.

Additional filtering is provided for the analog subsystem. In particular, a filter consisting of a pair of capacitors 708 and 710 and a resistor 712 is connected to a filter terminal VFILTER and analog ground AGND. Similarly, another pair of capacitors 714 and 716 and a resistor 718 are connected between a signal MFILTER and analog ground AGND.

The video controller 113A requires two separate clock signals: 14 MHz; and 32 KHz. The 14 MHz clock signal is used for most timing including the LCD panel memory and the bus cycle while the 32 KHz clock signal is used for video memory refreshing when the system is suspended. These clock signals are supplied by the clock generator 398 (FIG. 13) by way of the signal level translator 452 (FIG. 14). More particularly, 32 KHz and 14 MHz clock signals 32 KHz and 14 MHz from the clock generator 398, respectively, are applied to the signal level translator 452 to transform these respective signals into 5-volt signals 32 KHz.sub.-- 5V an 14 MHz.sub.-- 5V to provide a suitable clock signal voltage for the video controller 113A.

RGB data from the video controller 113A (FIG. 19) is supplied to the LCD screen 113C by way of a data bus PDATA[0..17]. This data bus PDATA[0..17] is applied to a plurality of current limiting resistors 708-742, respectively, to generate the buffer signals PDBUF[0..17]. These buffer signals PDBUF[0..17] are connected to the LCD panel 113 along with various control signals by way of a pair of connectors 732 and 734.

The BIOS as well as other data is stored in flash memory, for example, 512K by 8-bit memory devices 742-748 (FIG. 25). These flash memory devices 742-748 are connected to the local ISA bus 150 by way of the system address bus SA[0..23] and the system data bus SD[0..15]. The chip enable pins CE of the flash memory devices 742-748 are selected by a decoder circuit (FIG. 17), as will be discussed in more detail below. The output enable pins OE on the flash memory devices 742-748 are under the control of a memory read signal MEMR. The memory read signal MEMR is under the control of the system controller 129. The write/enable pins WE, which are active low, are under the control of a memory right gate signal MEMWGATE. This signal MEMKGATE is only enabled when the flash memory devices 742-748 are being programmed. As discussed above, programming of the flash memory devices 742-748 is under the control of a flash program signal FLASHVPP, available at port 0.3 of the keyboard controller 125 (FIG. 15). This programming signal FLASHVPP, normally pulled high by a pull-up resistor 749 (FIG. 17), is ORed with a memory write signal MEMW by way of an OR gate 751 to generate a signal MEMGATE, an active low signal.

The power supply for the flash memory devices 742-748 is developed by a 5-volt power supply signal 5V.sub.-- ROM. The 5-volt power supply signal 5V.sub.-- ROM is available from the DC converter 300 (FIG. 20) by way of a ferrite bead inductor 751. This power supply signal 5V.sub.-- ROM is also connected to a plurality of by-pass capacitors 752-758, for stabilization.

Decoding of the flash memory devices 742-748 is provided by the circuitry that includes the buffers 760, 762, the inverters, 764, 766, and 768 and OR 770 and a 3- to 8-bit multiplexer, Model No. 74HCT138, for example, as manufactured by Motorola and a pair of resistors 772 and 774 (FIG. 17). In particular, the system address bits SA[19..21] are applied to a 3- to 8-bit multiplexer 776. The system address bit SA18 is applied to the inverter 760 to develop a FLIP.sub.-- SA18 signal that is pulled down by the pull-down resistor 774. During a normal boot-up, the FLIP.sub.-- SA18 signal will be same as the system address bit SA18. However, during a test mode boot-up, the FLIP.sub.-- SA18 signal will be low until a control signal available at the control signal GPI00, available at the system controller 129, goes low in order to enable the system to boot from the BIOS in the flash memory device 742 as will be discussed in more detail below. Once the GPI00 signal goes low, the FLIP.sub.-- SA18 signal will be the same as the system address bit SA18.

The multiplexer 776 is under the control of a flash memory rewrite signal MRW. This signal MRW and the system address bit SA[23]. The flash memory read write signal MRW is under the control of an OR gate 780. The OR gate 780, in turn, is under the control of memory read and write signals MEMW and MER, which are applied to a pair of inverters 782 and 784, respectively, and, in turn, to the OR gate 780. The memory read MEMR and memory write MEMW signals are available from the system controller 129.

The output of the multiplexer 776 is used to generate the chip select signals CS60, CS68 and CS70. In order to provide the ability of the flash memory device 742 to be addressed during a test mode, the chip select signal CS78 is under the control of an OR gate 770 and a plurality of inverters 764-768. During a normal mode of operation, the chip select signal CS78 will be under the control of the multiplexer 776. During a normal boot up, the chip select signal CS78 for the flash memory device 742 will be under the control of a ROM chip select signal ROMCS, available at the system controller 129 in order to enable the system BIOS to be shadowed into the DRAM 111A.

In order to provide the ability of the system to update the BIOS in the flash memory device 742 and to recover from a corruption of the BIOS data in the flash memory device 742, a uniform asynchronous receiver transmitter (UART) 788 (FIG. 23) is provided. The UART 788 is connected to the system data bus SD[0..15] and the system address bus bits SA[0..2]. The UART 788 is powered by the 5-volt power signal 5V.sub.-- CORE, available at the DC-to-DC converter 320 (FIG. 26). A 1.84 MHz clock signal, 1.84 MHz.sub.-- 5V, available at the signal level translator 452, is used to drive the UART 788.

A serial interface 790 (FIG. 30), consisting of a standard DB-9 connector, enables external serial data to be received by the UART 788 (FIG. 23). The UART signals are filtered by way of a plurality of resistors 792-806 and bypass capacitors 802-822 and applied to an optional disaster recovery adapter 824, an RS-232 interface, connected to the rear of the DB-9 connector 790 and permits the flash memory devices 742-748 (FIG. 25) to be updated by an external source in the event of a flash disaster. The flash recovery adapter 824 may be implemented as a DB-9 connector and is connected to the 5-volt power supply 5V.sub.-- CORE, which, in turn, is connected to a plurality of bypass capacitors 826 and 828. An additional four capacitors 830-836 are connected to the module 824 as shown.

The power supply for the system includes the DC-to-DC converter 300 which has the ability to provide both 3volt and 5-volt power supplies signals to the various subsystems as discussed. The DC-to-DC converter includes a switching power supply 850, for example, a Maxim type 786. One source of power to the DC-to-DC converter 300 is the IBP 130, for example, 7.2 volts nominal, as well as from an external source of AC power connected to the plug 633 (FIG. 29).

Input power to the DC-to-DC converter 300 may be from an AC/DC converter (not shown) connected to the plug 633, which has a DC output voltage between 5.5-15 volts DC, applied to a power supply terminal AC/DCIN (FIG. 28) as well as internal batteries, for example, the IBP 130, connected to the system by way of a connector 850 (FIG. 26). The battery supply voltage from the IBP 130 is connected to the battery positive terminal BATT (FIG. 28). The two supplies BATT and AC/DCIN are alternatively used to develop a main power signal POWER (FIG. 28), that is applied to a switching power supply 851, for example, a Maxim type 786 by way of a pair of FETS 854 and 856 (IL. 26), under the control of a main power switch 855 (FIG. 28). The main power signal POWER is applied to a drain input D2 on each of the FETS 854 and 856. A bypass capacitor 860 is connected to the drain terminal D2 of the FET 856 and system ground. The source terminals S2 of each of the FETS 854 and 856 is connected to the switching power supply 851 to provide 5- and 3volt references by way of the zener diodes 860 and 862, respectively. The gate terminals G1 and G2 of the FETS 854 and 856 are under the control of the switching power supply 851.

The switching power supply 851 provides both a 3-volt and 5-volt output voltages 3V.sub.-- CORE and 5V.sub.-- CORE by way of filters which include a plurality of resistors 866 and 868, a plurality of inductors 870 and 872, and a plurality of capacitors 874-882 as well as a capacitor 879. For proper operation, the D1 and D2 terminals on the switching power supply 851 are connected to the system ground along with the ground pins PGND and GND. The SS3 and SS5 pins are connected to system ground by way of a pair of capacitors 884 and 886.

The frequency of the switching power supply 851 is under the control of a pair resistors 888 and 890 and a capacitor 892, connected to the SYNC and reference terminals on the switching power supply 851. A HOOK-VCC signal is applied to the VH and VL pins of the switching power supply 851. This signal HOOK-VCC is available from the module 894 (FIG. 29), discussed above. The signal HOOK-VCC signal is connected to the switching power supply 851 by way of a resistor 896 (FIG. 26); a plurality of capacitors 898, 900 and 902; and an FET 904.

As mentioned above, both the pen controller 110A (FIG. 21) and keyboard controller 125 (FIG. 15) are used to develop a shutdown signal SHUTDOWN. The shutdown signal SHUTDOWN is pulled low by a pull-down resistor 906 and applied to an active low shutdown pen SHDN* on the switching power supply 851. The shutdown signal SHUTDOWN (FIG. 20) is indicative of a shutdown by the keyboard controller 125 (FIG. 15).

As mentioned above, one source of power for the system is the IBP 130 which accounts for temperature and discharge rates and sends it to the keyboard controller 125 (FIG. 15). Two predefined levels are set in the IBP 130 to indicate low battery and critical battery. The IBP 130 will inform the keyboard controller 125 of a low battery when there is approximately five minutes left. When the battery charge is between 5 minutes to 2 minutes, the IBP 130 will report a battery critical condition. Within the final thirty seconds the IBP 130 will force an immediate shutdown. The IBP 130 will report the battery status approximately once every 2.5 seconds. If the system is changing to a power savings mode, a command will be sent to the IBP 130 to put the IBP 130 into a power-saving state. The IBP 130 will tri-state its communication lines and discontinue reporting battery status to the system.

A charge control signal CHGCTRL from the IBP 130 is used to control charging. Referring to FIG. 28, the charge control signal CHGCTRL is applied to a zener diode 910, for example, a 5.1V zener diode. The zener diode 910 controls whether the IBP 130 is fast charged or trickle charged as a function of the magnitude of the charge control signal CHGCTRL.

In particular, if the magnitude of the charge control signal CHGCRL is less than the zener breakdown voltage (i.e., less than 5.1 volts), the IBP 130 is trickle-charged by way of series pass transistor 912, a pair of resistors 914 and 916 from the external power signal POWER by way of a diode 918, a fuse 920 and a filter consisting of an inductor 922 and a capacitor 924.

Should the charge control signal CHGCTRL be greater than the zener breakdown voltage of the zener diode 910, the IBP 130 will be fast charged by way of an FET 928 whose source terminal is connected to the AC/DC converter by way of the diode 918 and drain terminal, connected to the battery positive terminal BATT by way of the fuse 920 and the inductor 922.

The series pass transistor 912 that controls trickle charging is under the control of an FET 930. The drain terminal of the FET 930 is connected to the system ground while the source terminal is connected to the base terminal of the PNP series pass transistor 912. Normally, the series pass transistor 912 is turned off with its base terminal being high by way of its connection to a pair of biasing resistors 932 and 934, which, in turn, are connected to the main power signal POWER by way of the diode 918. When the charge control signal CHGCTRL is less than the breakdown voltage of the zener diode 910, the charge control signal CHGCTRL turns on the FET 930 by way of the biasing resistors 936 and 938 a coupling capacitor, connected to its gate terminal. Once the FET 930 is turned on, it, turns on the series pass transistor 912 to provide a charging path between the main power signal POWER and the battery positive terminal BATT.

As mentioned above, fast charging of the battery is under the control of the FET 928. The FET 928, in turn, is under the control of a PNP transistor 926. The PNP transistor 926, which includes a pair of biasing resistors 940 and 942, is connected to the collector terminal of an NPN transistor 942. The base of the NPN transistor 942 is connected to a pair of biasing resistors 944 and 946 and, in turn, to a collector terminal of another NPN transistor 948 and the main power signal POWER. The NPN transistor 948 is biased by way of a pair of biasing resistors 950 and 952 and, in turn, to the anode of the zener diode 910.

In operation, when the charge control signal CHGCTRL exceeds the breakdown voltage of the zener diode 910, the zener diode 910 conducts thereby biasing the NPN transistors 942 and 948, turning them ON. Once the NPN transistor 942 is turned ON, the base terminal of the PNP transistor 926 is connected to ground, thereby turning the PNP transistor 926 ON. The PNP transistor 926, in turn, connects the main power signals POWER to the gate terminal of the FET 928 by way of the diode 918, thereby turning the FET 928 ON to enable the battery positive terminal BATT to be fast charged from the AC-to-DC converter.

As mentioned above, the wireless interface device 100 includes a radio system which allows for wireless interfacing with a host computer and also wireless interfacing to both a wired local area network (LAN) and a wireless LAN. The radio subsystem has been discussed above. It is implemented by way of an interface 960 (FIG. 16), implemented by way of a 25.times.2 header, which connects the radio subsystem to the balance of the circuitry in the wireless interface device 100. In particular, the system data bus SD[0..15], as well as the system address bus bits SA[0..2] are connected to the interface 960. The radio interface 960 is under the control of the system controller 129 (FIG. 12), such as I/O write (IOW), I/O read (IOR) and an address enable signal (AEN).

Output signals from the radio interface 960 include the signals CD.sub.-- LED, TX/RX.sub.-- LED, IRQ10 and IOCS16. As discussed above, the signal CD.sub.-- LED indicates a connection has been made with a host computer 101. The signal TX/RX.sub.-- LED indicates that a signal is either being sent or received through the radio interface 960. As mentioned above, the peripheral controller 128 (FIG. 13) is responsible for interrupt control. Thus, the radio subsystem interrupt IRQ10 is applied to the peripheral controller 128. Power supply for the radio interface 960 is by way of a 5-volt power supply signal 5V.sub.-- CORE, available at the DC-to-DC converter 300 (FIG. 26), which is filtered by a pair of bypass capacitors 962 and 964.

The interrupts for both the radio interface 960 IRQ10, as well as the UART 788 (FIG. 23) IRQ4, are formed into a common signal IRQ10/4 and applied to the system controller 129 by way of a resistor 966. In particular, the radio interface interrupt signal IRQ10 is applied to an inverter 962, whose output is ORed by way of the OR gate 964 with the UART 788 interrupt signal IRQ4. The output of the OR gate 964 forms the combined interrupt signal IRQ10/4.

The radio interface 960, as well as the UART 788 (FIG. 23), are selected by the chip select signals RADIOCS and URTCS. These signals are available at the output of a pair of the OR gates 968 and 970, respectively. The system address bit SA3 is inverted by way of an inverter 972 and ORed with a general purpose chip select gate signal GPCS1GATE by way of the OR gate 970 to generate the UART chip select signal UARTCS. The system address bit SA3 is applied directly to the OR gate 968 and ORed with the general purpose chip select gate signal GPCS1GATE to generate the radio chip select signal RADIOCS. The general purpose chip select signal gate signal GPCS1GATE is available at the output of an OR gate 974. In particular, a general purpose chip select signal GPCS1, available from the system controller 129 (FIG. 12), is ORed with an output from pin 0 of port 0 of the keyboard controller 125 (FIG. 15) to cause the radio interface 960 to be addressed at addressed 3E0-3E7 and the UART 788 to be addressed at address 3EA-3EF. The signal KBC.sub.-- P00 is normally pulled up to the 5-volt power supply voltage 5V.sub.-- CORE by way of a pull-up resistor 976.

The pen controller 110A is illustrated in FIG. 21 and is adapted to cooperate with an analog-resistive type digitizer 106. The pen controller 110A includes a controller 980, for example a Motorola type MC68HC705J2 microcontroller, with the firmware being programmed within the part. The controller 980 communicates with the system by way of the system data bus SD[0..15]. In particular, serial data from a port PB6 on the controller 980 is applied to a shift register 982, which, in turn, is connected to an 8-bit parallel buffer 984, which, in turn, is connected to the serial data bus SD[0..15]. The controller 980 is adapted to be used with an analog-resistive touch screen digitizer, for example a drawing No. 8313-34 Rev. C4, as manufactured by Dynapro. XY information from the digitizer 106 is received by the controller 980 by way of a connector 986. The X and Y information from the digitizer is connected to a 12-bit analog-to-digital (A/D) converter and also applied to port PA5 of the microcontroller 980. In particular, the X- data from the digitizer is applied to the A1 terminal of the A/D converter 988 by way of a pull-up resistor 990 and an FET 992. The FET 992 is under the control of a charge pump 994, for example a Linear Technology Model No. LTC1157C58. The Y- data from the digitizer is applied to the terminal A1 of the A/D converter 988 by way of a current-limiting resistor 994. A pair of bypass capacitors 996 and 998 are tied between the terminals A0 and A1 of the A/D converter 988 and an analog ground PEN.sub.-- AGND. The X+, Y+, X-, Y-inputs from the digitizer are also applied to the controller ports PA[0..4] by way of a plurality of transistors 1000, 1006, 1010, 1016 and 1018; a plurality of resistors 1002, 1008, 1012, 1014, 1020, 1022, 1028, 1032 and 1034; an inductor 1004; and a plurality of capacitors 1024 and 1026. The transistor 1018, as well as the transistors 992 and 998, are used to prevent leakage in a suspend state.

Power from both analog and digital power supply and grounds are supplied to the system. In particular, a 5-volt digital power supply PEN.sub.-- VCC, developed from the 5-volt supply 5V.sub.-- CORE, is available from the DC-to-DC converter 300 (FIG. 26) by way of an in-line ferrite bead inductor 1028. An analog power supply PEN.sub.-- AVCC is developed from the digital supply PEN.sub.-- VCC by way of an inline ferrite bead inductor 1030. The digital power supply PEN.sub.-- VCC is applied to the microcontroller 980 and filtered by a bypass capacitor 1030. The analog supply PEN-AVC is utilized by the 12-bit analog-to-digital converter 988 and filtered by way of a bypass capacitor 1032.

A separate clock supply is used for the microcontroller 980. This clock supply includes a 4.0 MHz crystal 1034, a resistor 1036 and a pair of parallel coupled capacitors 1038 and 1040. The clock supply is applied to the oscillator terminals OSC1 and OSC2 of the microcontroller 980.

A 5-volt signal PENACT.sub.-- 5V, available at the port P5V pin of the microcontroller is converted to a 3volt signal PENACT.sub.-- 3V by way of a pair of voltage dividing resistors 1042 and 1044. This signal PENACT.sub.-- 3V is applied to a 3volt terminal of the system controller 129 (FIG. 12). As discussed above, the power supply for the FETs 992 and 1018 is provided by the charge pump 994. The power supply for the charge pump 994 is a 5-volt power supply signal 5V.sub.-- CORE, available at the DC-to-DC converter 300 (FIG. 26). A ground terminal of the charge pump 994 is connected to system ground by way of a pull-down resistor 1050. The 5-volt power supply PEN.sub.-- VCC is also utilized by the shift register 982 and the data buffer 984 and buffered by way of a pair of bypass capacitors 985 and 987.

The chip select signal PENCS for the data buffer 984 is generated by an OR gate 1052. The general purpose chip select signal GPCS2 is available from the system controller 129 (FIG. 12), as well as a signal KBC.sub.-- P00, available from the keyboard controller 125 (FIG. 15) are applied to the inputs of the OR gate 1052.

A pen shut-down signal PEN.sub.-- SHUTDOWN is used to develop a shut-down signal SHUTDOWN as discussed above for turning on the switching power supply 851 (FIG. 26). The pen shutdown signal PEN.sub.-- SHUTDOWN is developed by the circuit that includes the transistors 1060, 1062 and 1064; a plurality of resistors 1066, 1068, 1069, 1070 and 1072; and a capacitor 1074. In particular, a 5-volt power supply signal 5V.sub.-- CORE is applied to a pair of voltage-dividing resistors 1070 and 1072, which, in turn, is used to bias the transistor 1064 on. The base-emitter voltage is held fairly constant by the capacitor 1074. Once the transistor 1064 is turned on, it is used to control the FET 1062. A main power supply signal POWER is applied to the gate of the FET 1062 by way of the resistor 1069. Wake up of the system by way of the pen subsystem is discussed below.

As mentioned above, the wireless interface device 100 includes the flash memory devices 742-748 (FIG. 25). As will be discussed in more detail below, the flash memory devices enable user software upgrades by way of the radio interface 960 (FIG. 16). Should power be lost during the programming, the data within the flash memory devices 742-748 will be corrupted, which could result in the system failing to boot.

In order to enable recovery from such a condition, recovery BIOS is stored in a protected sector of the flash memory device 742, which will be unaffected during reprogramming. In addition, a serial port interface 790 (FIG. 30) is provided to enable the flash memory devices 742-748 to be programmed in such a condition by an alternative wired source following a normal boot-up. Unfortunately, the configuration of the flash memory device 742 may result in the system failing to boot. More particularly, disaster recovery BIOS is not stored at the uppermost address of the flash memory device 742. Each flash memory device 742-748 are 512K.times.8-bit devices. With reference to Table 5 above, the flash memory device 742 is mapped to the address range $0C0000-$0FFFFF. The recovery BIOS is contained in the lower half of that range (i.e. $0E0000-$0FFFF).

On a normal boot-up, the system begins executing code at the top of the address range (i.e. $0C0000-ODFFFF) flash memory device 742 by way of the system address bit SA18. More particularly, on a normal boot-up a test mode signal TEST.sub.-- MODE, available at port 1.1 of the keyboard controller 125 (FIG. 15) is pulled high by the keyboard controller 125 during boot-up, which enables the buffer 762 (FIG. 17) which, in turn, enables another buffer 760 to enable the system address bit SA18 during boot-up. When the system address bit SA18 is enabled, the system begins executing code at the top of the address range ($0C0000) of the flash memory device 742. However, during a condition when the data in the top half of the address range ($0C00000-ODFFFFF) becomes corrupt as a result of a problem occurring during reprogramming, the system may not boot during such a condition.

In order to solve this problem, the system address bit SA18 is forced low. By forcing the system address bit SA18 low, the system will begin executing code from the protected area of the flash device 742 in the address range ($0E0000-$0FFFF) during such a condition where the disaster recovery BIOS resides in a protected sector. In particular, the system address bit SA18 is applied to the buffer 760 (FIG. 17), which is under the control of the test mode signal TEST.sub.-- MODE by way of the buffer 762. The output of the buffer 760 is a signal FLIP.sub.-- SA18, which is applied to the address pin A18 (FIG. 25) on the flash memory device 742.

During a normal boot-up, the test mode signal TEST.sub.-- MODE will enable the buffer 762 (FIG. 17) and, in turn, the buffer 760 to cause the system address bit SA18 to drive the signal FLIP.sub.-- SA18. During a condition when the code in the flash memory device 742 becomes corrupt, the test mode signal TEST.sub.-- MODE is forced low, which, in turn, forces the signal FLIP.sub.-- SA18 low, resulting in the system executing code from the protected area (i.e. $0E0000-OFFFF) of the flash memory device 742 during such a condition to enable the flash memory device 742 (FIG. 25) to be reprogrammed by way of the serial interface 790 (FIG. 30).

There are various ways in which to force the test mode signal TEST.sub.-- MODE low during reprogramming of the flash memory device 742 by way of the serial interface 790. One way is to externally ground the test mode signal TEST.sub.-- MODE during such a condition. In particular, the test mode signal TEST.sub.-- MODE may be connected to one pin of a two-pin header 1100 (FIG. 30). The other pin of the header 1100 is connected to system ground. During reprogramming of the flash memory device 742, an external jumper (not shown) is inserted into the header 1100 to shunt the test mode signal TEST.sub.-- MODE to system ground to enable the system to execute code from the protected or boot block area of the flash memory device 742 in order to enable the system to be booted. Once the system is booted, the flash memory device 742 is reprogrammed by way of the serial interface 894 (FIG. 29). Once reprogramming is complete, the shunt is removed from the header 1100 (FIG. 30) and the adapter plug 790 is removed, restoring the system to normal operation.

In order to conserve battery power, the wireless interface device 100 goes into a suspend mode when the system is not in use. As discussed above, a shut down signal SHUTDOWN (FIGS. 20 and 26) is used to shut down the power supply 851 (FIG. 26) during such a condition, which essentially disables the power to all but the circuitry required to detect a pen down event by way of the main power signal POWER (FIG. 28).

Three sources control the shut down signal SHUTDOWN: the keyboard controller 125 (FIG. 15); the pen controller 110A (FIG. 21) and a signal HOOK.sub.-- VCC, connected to the switching power supply 851 (FIG. 26) by way of the FET 904. These sources are diode ORed to the shut down signal SHUTDOWN by way of the diodes 645 and 647 (FIG. 20) and a diode 1102 (FIG. 28). During a normal state, the shut down signal SHUTDOWN is high, which enables the power supply 851 (FIG. 26). When the shut down signal SHUTDOWN goes low, the power supply 851 goes into an inactive state. During the inactive state, minimum power is supplied to the pen detection circuitry as discussed above.

As will be discussed in more detail below, once the system is turned on by the main power switch 855 (FIG. 28), the shut down signal SHUTDOWN will be under the control of the pen shutdown signal PEN.sub.-- SHUTDOWN, available from the pen controller 110A (FIG. 21) and the keyboard controller shut down signal KBSHUTDOWN (FIG. 20).

The keyboard controller 125 (FIG. 15) can place the system in a suspend state by way of a command, which, in turn, causes the keyboard controller shut down signal KBSHUTDOWN, available at port P0.2, to go low. More particularly, during normal operation, only the keyboard shutdown signal KBSHUTDOWN is high, placing control of the suspend state solely in the keyboard controller 125. The keyboard controller 125 can then force the system into a suspend state by forcing port P0.2 low, which, in turn, places the power supply 851 (FIG. 26) in an inactive state.

The pen shut down control signal PEN.sub.-- SHUTDOWN is used to wake the system from a suspend state. More particularly, as mentioned above, during a suspend state, power from the main power supply POWER (FIG. 28) is applied to the collector of the transistor 1064 (FIG. 21) and to the drain of the FET 1062. Since the 5-volt power supply 5V.sub.-- CORE is unavailable during a suspend state, the transistor 1064 will be OFF, allowing power to appear at the gate of the FET 1062, thus turning the FET 1062 ON. Once the FET 1062 is turned ON, the main power signal POWER is applied to the XPLUS terminal of the digitizer panel. Thus, a pen (or finger) down event will result in the YPLUS terminal being connected to the XPLUS terminal by way of a finite resistance (i.e. 500-1500 Ohms) to apply power to the YPLUS terminal, which, in turn, is connected to the drain of the P-channel FET 1060 while its source is used as the pen shutdown signal PEN.sub.-- SHUTDOWN. The FET 1060 is under the control of a leakage signal LEAKAGE, available at the output of the charge pump 994. Since the leakage signal LEAKAGE will be low during a suspend state, the FET 1060 will turn on in response to the pen down event, thereby connecting the YPLUS terminal to the pen shut down signal PEN.sub.-- SHUTDOWN. As mentioned above, the YPLUS terminal will be high in response to a pen down event following a suspend state. As such, the pen shut down signal PEN.sub.-- SHUTDOWN will go high. Since the pen shut down signal PEN.sub.-- SHUTDOWN is diode ORed with the shut down signal SHUTDOWN, the shut down signal SHUTDOWN will thus be forced high in response to a pen down event following a suspend state, which, in turn, will wake up the power supply 851 (FIG. 26). Once the system is wakened, the keyboard controller shutdown line KB.sub.-- SHUTDOWN goes high, latching the system ON. The resistors 1070, 1072 and the capacitor 1074 are used to delay turning ON the transistor 1064 and the turning OFF of the FET 1062 before the keyboard shutdown signal KB.sub.-- SHUTDOWN is pulled high which would cause the pen shut down signal PEN.sub.-- SHUTDOWN to go low before the keyboard shutdown signal KB.sub.-- SHUTDOWN goes high.

The FETs 992, 998 and 1018 are used to prevent current leakage in a suspend state. In particular, these FETs 992, 998 and 1018 are under the control of the leakage control signal LEAKAGE, available at the charge pump 994, which turns the FETs 992, 998 and 1018 ON in normal operate and OFF in a suspend state.

The sensing of suspend state is done by the charge pump 994, which monitors the 5-volt power supply signal 5V.sub.-- CORE. When the 5-volt power supply signal 5V.sub.-- CORE goes low, indicating a suspend state, the leakage control signal LEAKAGE goes high, turning off the FETs 992, 998 and 1018, blocking leakage into the pen circuitry from the XPLUS terminal.

The system ON/OFF switch 855 (FIG. 28) enables the system to be completely shut off. When the switch 855 is closed, power from either the IBP 130 or the external AC-to-DC converter supplies power to the system. In order to wake up the system from an OFF state, a shutdown line SHUTDOWN must be held high until the keyboard controller 125 pulls its shutdown pin KB.sub.-- SHUTDOWN high. As discussed above, the keyboard shutdown signal KB.sub.-- SHUTDOWN is diode ORed relative to the shutdown signal SHUTDOWN, which controls the power supply 851 (FIG. 26). Until the time when the keyboard shutdown signal KB.sub.-- SHUTDOWN is pulled high, a signal HOOK.sub.-- VCC is used to force the shut down signal SHUTDOWN high. As mentioned above, the HOOK.sub.-- VCC signal is also diode ORed relative to the shutdown signal SHUTDOWN by way of the diode 1102 (FIG. 28). However, for proper operation of the system, the shutdown signal SHUTDOWN will be under the control of the keyboard controller 125 (FIG. 15) after the system is turned on. Thus, a 5-volt power supply signal HOOK.sub.-- VCC, available at the power supply 851 (FIG. 26), forces the shut down signal SHUTDOWN high until the keyboard controller 125 (FIG. 15) has time to pull its keyboard shutdown signal KB.sub.-- SHUTDOWN high. The 5-volt power supply signal HOOK.sub.-- VCC is always high when the main power switch 855 is turned on. On power-up, the 5-volt power supply signal HOOK.sub.-- VCC forces the shutdown signal SHUTDOWN (FIG. 28) high by way of an FET 1104 and the diode 1102, which, in turn, wakes up the power supply 851 (FIG. 26). Once the power supply 851 is enabled, a power supply signal MAX 786.sub.-- VCC is used to turn off the FET 1104 to place the control of the shut down signal SHUTDOWN under the control of the keyboard controller 125 as discussed above. In order to provide sufficient time for the keyboard controller 125 to pull its keyboard shutdown signal KB.sub.-- SHUTDOWN high, the turn OFF of the FET 1104 is delayed by way of a resistor 1106 and a capacitor 1108. In particular, once the main power switch 855 is closed, the power supply signal MAX786.sub.-- VCC will be low, thereby causing the FET 1104 to be turned ON, which connects the power supply signal HOOK.sub.-- VCC to the shutdown signal SHUTDOWN by way of the diode 1107. Once the power supply 851 is enabled, the signal MAX786.sub.-- VCC, applied to the gate of the FET 1104, turns off the FET 1104, placing the shutdown signal SHUTDOWN under the control of the keyboard controller shutdown signal KB.sub.-- SHUTDOWN as discussed above. The resistor 1106 and capacitor 1108 delay the turning off of the FET 1104 after the signal MAX786.sub.-- VCC goes high for a sufficient time to allow the keyboard controller 125 to pull its keyboard shut down signal KB.sub.-- SHUTDOWN high.

An inhibit circuit (FIG. 26), which includes a plurality of resistors 1110-1120, a diode 1122, a transistor 1124 and an FET 1126, is used to prevent the system from being turned ON during low battery conditions when the system is being supplied solely by the IBP 130. During a normal condition (i.e, when the system is being supplied power by the AC/DC converter or by the battery, the signal MAX786.sub.-- VCC is connected to the main power signal POWER by way of the FET 1126. The FET 1126 is under the control of the transistor 1124. During conditions when the AC/DC converter is supplying power to the system, a signal AC/DCTN will be high, thereby turning ON the transistor 1124, which, in turn, turns ON the FET 1126, connecting the main power signal POWER to the signal MAX786.sub.-- VCC. The collector of the transistor 1124, in turn, controls the FET 904, which connects the power supply signal HOOK.sub.-- VCC to the enable terminals ON3 and ON5 on the power supply 851. When AC power is not available, the AC/DCIN goes low, leaving the control of the transistor 1124 under the control of an inhibit signal INHIBIT, available from the IBP 130 by way of the connector 850. During a normal battery condition, the inhibit signal is high, keeping the transistor 1124 turned ON, thereby enabling the power supply 851 by way of the FET 904. Should a low battery condition occur, the inhibit signal goes low, turning OFF the transistors 904, 1124, as well as the FET 1126, to prevent the system from being turned ON.

As mentioned above, the wireless interface device 100 includes a digitizer 110B and utilizes a passive pen as an input device. FIGS. 31-35 illustrate a method for emulating the functions of a mouse, for example a two-button mouse, to provide standard mouse functions with the passive pen.

There are three aspects of the mouse emulation. One aspect relates to emulation of a double click of a mouse button, required by some application programs. Another aspect relates to emulating both the left and right buttons of a two-button mouse. The third aspect relates to emulating both the movement of the mouse (MOVE MODE) and the clicking of a mouse button (TOUCH MODE) with a passive pen as an input device.

Referring first to FIG. 31, the mouse emulation system is event-driven by the passive pen. Initially the system checks to see if the passive pen has touched anywhere on the LCD 113C (FIG. 36), which includes a display area 1200 and a hot icon area 1202. If a pen-down event has been detected, the system checks in step 1204 if the wireless interface device 100 has been placed in a calibration mode. If so, a calibration handler is called in step 1206. The calibration handler does not form part of the present invention. If the wireless interface device 100 is not in the calibration mode, the system then checks to determine if the pen has been lifted from the LCD 113C in step 1208. If a pen-up event occurs subsequent to a pen-down event, control is passed to a hot icon identification (ID) processor (FIG. 32) in step 1210, which, as will be discussed below, processes the pen position to determine which of the hot icons in the hot icon area 1202 of the LCD screen 113C was selected. If the pen was not lifted from the LCD 113C, the system checks in step 1212 if the previous event in a previous cycle was a pen-up event. If the previous pen event in the previous cycle was a pen-down event, the current pen event is processed by a mouse mode handler (FIG. 33) in step 1214, which, as will be discussed in more detail below, determines if the pen is being used in a mouse MOVE or mouse TOUCH MODE. In step 1216, the coordinates of the current pen-down event are processed to determine if the current pen-down event occurred in the hot icon area 1202 of the LCD 113C. If the pen-down event occurred in the hot icon area 1202 (FIG. 36), a flag is turned on indicating the hot icon area 1202 was selected in step 1218. If the system determines the current pen-down event occurred in the display area 1200 (FIG. 36) of the LCD screen 113C, an audio click is generated in step 1220; different from the hot icon audio click.

Steps 1204-1220 are driven by each pen event in order to determine the location of the pen-down event (i.e. hot icon area 1202 or display area 1200). Once the system determines where the pen event occurred, the pen data is converted to mouse data in step 1222 and a cursor is displayed in the viewing area 1200, corresponding to the location of the pen touch in step 1224. After the cursor is displayed, the system determines in step 1226 whether the mouse data is to be used locally by the wireless interface device 100 for local applications or the application running on the host computer 101. As mentioned above, the wireless interface device 100, through its graphical user interface, provides a virtual or on-screen keyboard (OSK). Thus, if the OSK has been activated and the pen event occurs in the OSK area, the mouse data is used locally by the wireless interface device 100 in step 1228. If the wireless interface device 100 is running a host application, the mouse data is sent to the host computer 101 application over the wireless interface as discussed above in step 1230.

As mentioned above, the system is able to emulate both left and right mouse buttons. This emulation is accomplished by way of left/right mouse button hot icon 1232 (FIG. 37). A left mouse button is configured to be the default setting. This hot icon 1232 is set up as a toggle. Thus, when the system is first turned on, the pen events from the mouse mode handler are translated to be left mouse button events. Anytime the left/right mouse button hot icon 1232 is selected, the system will toggle and translate subsequent pen events to be right mouse button events. A subsequent pen-down event on the hot icon 1232 causes subsequent pen events from the mouse mode handler to be translated as left mouse button events and so on.

The hot icons in the hot icon area 1202 (FIG. 36) are triggered by a pen-down event followed by a pen-up event. As discussed above, such a sequence of pen events is processed by hot icon ID processor 1210, illustrated in FIG. 32. The hot icon ID processor 1210 first determines if the pen event occurred in the viewing area 1200 (FIG. 36) of the LCD 113C by determining from the mouse mode handler 1214 (FIG. 33) whether the system is in the TOUCH in step 1234, since this mode only occurs for pen events in the viewing area 1200 of the LCD display 113C. If the system is not in a TOUCH mode, the system checks in step 1236 whether the system is in the MOVE mode. If the pen event (i.e. pen-down followed by a pen-up event) did not occur in the viewing area 1200 of the LCD display 113C, the system compares the coordinates of the pen-down event with the locations of the various hot icons displayed in FIG. 37 in step 1238. In step 1240 (FIG. 32), the system determines if the left/right mouse button hot icon 1232 was selected. If not, the system proceeds directly to step 1242 to uplevel software for processing. If the system determines that the left/right mouse hot icon 1232 was selected, the system emulates a left or right mouse button in step 1244, depending on the last status of the left/right mouse button emulation and utilizes the emulated left or right mouse button status in the uplevel software in step 1242.

Pen events in the hot icon area 1202 of the LCD display 113C are handled by the hot icon ID processor 1210 (FIG. 32), while pen events in the viewing area 1200 are handled by the mouse mode handler 1214 (FIG. 33). The mouse mode handler 1214 emulates two mouse actions: moving without either button being depressed and released (MOVE); and button depression and release events (TOUCH). As discussed above, both left and right mouse button events can be emulated in the TOUCH.

As discussed above, a current pen-down event preceded by a pen-down event activates the mouse mode handler 1214 (FIG. 33). In step 1246, the system first determines if the hot icon flag is on. As discussed above, the hot icon flag is turned on anytime a pen-down event occurs in the hot icon area 1202 (FIG. 36) of the LCD display 113C. If the hot icon flag is not on, the pen-down event is translated to a mouse button down event by a mouse TOUCH handler in step 1248. If the hot icon flag is on, the system determines in step 1250 whether the coordinates of the current pen-down event to determine if the current pen-down event occurred in the hot icon area 1202. If so, the pen coordinate data is dropped in step 1252 since such data will be processed by the hot icon ID processor 1210 (FIG. 32), discussed above. If the current pen event occurred in the viewing area 1200, the pen coordinate data is translated to mouse move data.

A mouse button double click is emulated by two pen-down events separated by a pen-up event in the viewing area 1200 of the LCD 113C. In particular, when the host computer 101 is running a Windows application, a pen driver translates the two pen-down events separated by a pen-up event and passes four mouse messages: mouse button down; mouse button release, mouse button down and mouse button release to the host Windows application.

As will be discussed in more detail below, the host manager Windows module 1260 modifies a Windows configuration file. (WIN.INI) and, in particular, the distance and time limitations for a mouse button double click. In particular, the Windows system checks the Windows configuration file WIN.INI in order to compare the distance between the mouse locations for each of the clicks as well as the time between clicks. More particularly, the Windows systems will only pass double click data to a Windows application program if the distance (i.e. height and width) between mouse locations for the two clicks is less than 16 for both height and width and the time between the clicks is less than 1.0 seconds.

With a pen-based system two pen-down events separated by a pen-up event normally take longer and occur at greater distances between pen-down events than allowed by the Windows system to generate a double click. Thus, the host manager Windows module 1260 modifies the time and distance parameters to enable two pen-down events separated by a pen-up event to enable Windows to emulate a mouse double click that can be passed on to the Windows application program running in the host computer 101. In particular, the host manager Windows module 1260 includes an initializer 1262 which loads the host manager Windows module 1260, and an initial icon displayer 1264, which displays that the host manager Windows module 1264 has been loaded. The host manager Windows module 1260 also includes a double click configuration modifier 1266. The double click configuration modifier 1266 modifies the configuration of the Windows systems file WIN.INI by modifying the time or speed in step 1268. The distance, broken down into width and length, between the successive pen-down events, is modified by a double click width modifier and a double click height modifier in steps 1270 and 1272. The modified speed, width and height parameters are set in the Windows system file WIN.INI running in the host computer 101 in step 1274 to enable a mouse button double click to be emulated by two successive pen-down events.

Normally, the Window system file WIN.INI is in cache. The host manager Windows manager disables the in cache copy of the Windows system file WIN.INI, which allows the Windows system to go to the modified configuration file with the modified parameters.

As mentioned above, the wireless interface device 100 connects to a host computer 101 and displays whatever is being displayed on the host computer 101. In particular, after a connection is made, all of the screen images on the host computer 101 are passed on to the LCD display 113C on the wireless interface device 100. Whenever the host computer 101 is running a screen saver, the host display will continually change, passing on all of the images to the LCD 113C on the wireless interface 100, which creates a lot of unnecessary traffic on the LAN. In order to reduce this unnecessary LAN traffic, a host manager Windows module 1278 (FIG. 39) disables the screen saver on the host computer 101 anytime a connection is made between the host computer 101 and the wireless interface device 100. Anytime the connection between the host computer 101 and the wireless interface device 100 is broken, the host manager Windows module re-enables the screen saver on the host computer 101.

The connection status between the host computer 101 and the wireless interface device 100 is under the control of a host manager DOS module 1280 (FIG. 38), a terminate and stay resident program. The host manager DOS module 1280 is driven by a timer tick interrupt and checks the connection status at each timer tick interrupt. If the connection status has changed, the host manager DOS module 1280 calls a host manager communicator 1282, which passes the new status to the host manager Windows module 1278.

Referring to FIG. 39, anytime the connection status between the host computer 101 and the wireless interface device 100 changes, the host manager Windows module 1278 checks the new status in step 1284. If the connection has been lost, a screen saver disable module 1286 is called, which, in turn, calls several Windows modules: Windows Software Development kit functions; SystemParametersInfo; and WritePrivateProfileString to disable the screen saver. Should the current status indicate that the wireless interface device 100 is connected to the host computer 101, the system proceeds to step 1288, which calls the various Windows module.

Referring to FIG. 40, anytime the host manager DOS module 1280 is loaded, an initial connection status checker 1290 calls the host manager DOS module 1280 to obtain the current connection status between the wireless interface device 100 and the host computer 101. Next, the system checks in step 1292 whether a connection exists between the host computer 101 and the wireless interface device 100. If not, the system returns. If there is a connection, a virtual key poster 1294 posts a virtual key V.sub.-- TAB into the Windows Systems queue to force the Windows program to disable the current active screen saver automatically, which, in essence, simulates the press of a key on a keyboard. Once the current active screen saver is disabled, the screen saver on/off flag in a Windows configuration file is turned off in step 1296 to disable the screen saver until there is a change in the connection status.

Whenever a connection is made between wireless interface device 100 and the host computer 101, the user can optionally blank the screen on the host computer 101 and disable the keyboard and mouse inputs connected to the host computer 101. These features prevent the host computer 101 from being accessed while the host computer 101 is under the control of the wireless interface device 100 at a remote location. Once the connection between the host computer 101 and the wireless interface device 100 is lost, the keyboard and mouse inputs on the host computer 101 are re-enabled under the control of the host manager program residing in the host computer 101.

There are certain situations where the screen to the host computer 101 may not be enabled on disconnection, for example, when the disconnection occurs because the wireless interface device 100 is either out of power or out of range. In order to enable the user to access the host computer 101 in such a situation, a host manager 1300 (FIG. 40A) first checks whether the connection status has changed in step 1302 in the manner as discussed above. If the system is connected, no action is required. However, if the connection has been broken, the system checks in step 1304 whether the screen is enabled. If not, the user will have normal access to the host computer 101. If so, the latest log-in password by the user is stored in by the system in step 1306. Since the host manager DOS module controls the screen, the system checks in step 1308 to determine whether Windows is running in the host computer 101. If DOS is running, the system compares the password entered on the keyboard with the latest log-in password in steps 1310 and 1312. If the password entered does not match the correct password, the system returns to step 1310 and awaits another keyboard input. If the correct password is entered, the screen is turned on in step 1314.

Should the host computer 101 be running Windows, as determined in step 1308, the latest log-in password is passed to a host manager Windows module in step 1316. The system next checks in steps 1318 and 1320 whether the correct password was entered in a similar manner as discussed above. If so, since DOS handles the enabling of the screen on the host computer 101, the host manager DOS module is notified that the correct password was entered in step 1322, which, in turn, enables the screen in step 1314.

The pen controller 110A (FIG. 21) normally generates a series of interrupts and, in turn, a series of pen packets whenever the pen touches the LCD 113C (a pen-down event) and is lifted from the LCD 113C (a pen-up event) and generates an interrupt. For each interrupt, a single packet is generated. The format of the possible packets is illustrated in Table 7 below, where x0 is bit 0 of the x coordinate of the pen location and y0 is bit 0 of the y coordinate of the pen location, etc.

The packets are generated in the following sequence (p1, p2, p3, p4), (pi, p2, p3, p4) . . . (p1, p2, p3, p4), (p5). The packets p1, p2, p3, p4relate to pen-down events (a pen point); each group of packets (p1, p3, p3, p4) relating to one x-y coordinate of the pen. The packet p5 relates to a pen-up event. Thus, anytime the pen is lifted from the digitizer, one packet p5 is generated. Thus, when the pen first touches the digitizer panel and is moved across the digitizer, a plurality of pen points (p1, p2, p3, p4) are generated which correspond to the x, y locations of the points touched by the pen. Normally 110 pen points per second are generated by the pen controller 110A.

Whenever a 12-bit serial pen packet is generated by the pen controller 110A and read by a firmware module in step 1330 (FIG. 41), an interrupt is generated in step 1332. A pen packet assembler assembles the packets into pen points (p1, p2, p3, p4). These pen points (p1, p2, p3, p4) are processed and passed to the applications program. In order to process each pen point (p1, p2, p3, p4), the interrupts must be disabled. During the time when the interrupts are disabled, the pen point packets (p1, p2, p3, p4) and the pen-up packets p5 are generated by the pen controller 110A but not processed and thus are garbled or lost. Lost or garbled pen point packets (p1, p2, p3, p4) do not affect mouse emulation. However, since mouse emulation is based on both pen-down and pen-up events, lost pen-up packets p5 can result in the mouse emulation being hampered, possibly resulting in the system being stuck in the state preceding the pen-up event.

In order to solve this problem, a firmware module 1330 generates two pen-up packets p5. More particularly, with reference to FIG. 42, the firmware module 1330 reads in the 12-bit serial data from the pen controller 110A into packets in step 1334. Next, the system checks in step 1336 whether the packet was a pen-up packet p5. If not, the system proceeds to the pen driver in step 1332 (FIG. 41). If the packet is a pen-up packet p5, the system checks to determine if the pen-up packet p5 is the first pen-up packet in step 1338. If not, the system passes the packet to the pen driver in step 1332 as discussed above. If the system determines in step 1338 that the pen-up packet p5 is the first pen-up packet p5, the serial data for second pen-up packet p5 is generated in step 1340 and assembled in step 1334. In addition, the first pen-up packet p5 is passed to the pen driver.

The pen driver 1332 (FIG. 43) is responsive to an interrupt that is generated each time a packet is assembled. In response to an interrupt, the pen driver reads the packet in step 1342. In step 1344, the pen driver determines whether the packet is a pen-up packet p5. If not, the pen packet assembler processes the packet in step 1346. If the system determines in step 1344 that the packet is a pen-up packet, it next checks in step 1346 whether the packet is the second pen-up packet. If so, indicating that the first pen-up packet was processed, the second pen-up packet is dropped in step 1348. If not, the packet is determined to be a first pen packet, which is processed by the pen packet assembler in step 1346.

The wireless interface device 100 may be connected to host computer 101 by way of a wireless LAN. The wireless LAN protocol is Novell open data link interface IPXODI protocol. Since the IPXODI protocol is also used for wired LAN's, it would be desirable to connect the wireless interface device 100 to a wired LAN system and utilize the Novell IPXODI protocol. Unfortunately, the IPXODI protocol can only communicate with a single LAN card at a time, either a wired LAN card or a wireless LAN card at one time.

The standard Novell LAN stack configuration is illustrated in FIG. 45. The LAN card is identified with the reference numeral 1352. Communication between the LAN card 1352 and the IPXODI protocol is by way of a driver 1354. The driver 1354 communicates with the IPXODI protocol (IPXODI.COM) 1355 by way of a link support layer LSL.COM 1356. The Novell IPXODI protocol passes data between the applications programs 1358 and the link support layer LSL.COM 1356. Even though the link support layer LSL.COM can support multiple LAN cards, the IPXODI protocol only supports a single LAN card.

In order to enable the Novell IPXODI protocol to support a configuration as illustrated in FIG. 44 to enable the wireless interface device 100 to connect to both a wired LAN card 1352 and a wireless LAN card 1360, an additional layer IPXMUX.COM (FIG. 46) is provided for multiplexing incoming and outgoing packets to and from the wired LAN card 1352 and the wireless LAN card 1360. The multiplexer IPXMUX.COM manipulates the data packet source and destination addresses to simulate a single LAN card so as to be compatible with the IPXODI protocol. By providing the additional layer IPXMUX.COM, the host computer 101, as well as the wireless interface device 100, will be able to access all of the LAN resources 1350 (FIG. 44).

Referring to FIG. 46, the additional layer IPXMUX.COM is stacked between the Novell IPXODI protocol IPXODI.COM 1355 and the link support layer LSL.COM 1356. As mentioned above, the link support layer LSL.COM 1356 can support two LAN cards. Thus, a wireless LAN card 1360 and a corresponding wireless LAN card driver 1362, which communicates with the link support layer LSL.COM 1356 along with the wired LAN card 1352 and its corresponding driver 1354, can communicate with IPXODI.COM by way of the driver.

The multiplexer IPXMUX.COM 1364 multiplexes or interleaves the data from both the wireless LAN card driver 1354 and the wired LAN card driver 1362 to the IPXODI protocol by manipulating the source and destination addresses of incoming and outgoing packets, so that as far as the Novell IPXODI protocol is concerned, it is only communicating with a single LAN card. Similarly, communication from the host computer 101, as well as applications 1358, which may be running on the wireless interface device 100, to both the wired LAN card 1352 and the wireless LAN card is formatted by the IPXODI.COM and multiplexed to either the wireless LAN card 1360 or wired LAN card 1352 by the multiplexer IPXMUX.COM by way of the link support layer. The multiplexer IPYMUX.COM 1364 is loaded after the wired LAN card driver 1354 and the wireless LAN card driver 1362 are loaded and before IPXODI.COM 1355.

The Novell LAN software includes a configuration file which checks the particular LAN cards 1352 being run by the LAN card driver 1354. The system is initialized by the routine illustrated in FIG. 47, which is run each time the multiplexer IPXMUX.COM 1364 is loaded. Initially, a command line parser 1366 is used to determine whether the user has issued commands to either load or unload IPXMUX.COM command in step 1368. If the command is an unload command, the system checks whether IPXMUX.COM 1364 has already been loaded in step 1370. If so, the system unloads IPXMUX.COM 1364 in step 1372. If IPXMUX.COM 1364 has not been loaded, the system exits the initialization routine.

If the command was to load IPXMUX, the system checks in step 1374 to determine if the link support layer LSL.COM 1356 has been loaded. If not, the system exits the initialization routine since IPXMUX.COM cannot be loaded until the link support layer LSL.COM has been loaded. If the link support layer LSL.COM 1356 was loaded, control is passed to a LAN configuration browser in step 1376 to browse the LAN configuration for the number of LAN cards and the frame types of the cards and the number of frame types (i.e. IEEE 802.2, 802.3, etc.) to find out which LAN card drivers are running. In addition, the browser finds and saves all relevant application program interface entry points to the link support layer LSL.COM and sets to those supported by IPXMUX.COM. The browser also sets the LSL interrupt vector to the interrupt vector supported by IPXMUX.COM, as well as finds and saves all logical board numbers.

In order to interleave the data from the wired LAN card 1352 (FIG. 46) and the wireless LAN card 1360 to IPXODI.COM to emulate a single LAN card, 2F interrupt calls from the application program by way of IPXODI.COM are trapped and handled by a separate routine. In particular, 2F interrupt calls are checked in step 1378 to determine if such calls are interrupt calls to LSL.COM. If not, the system exits. If so, the address of the LSL protocol support API handler supported by IPXMUX.COM is returned. Interrupt calls to LSL.COM from an application program are handled by a special interrupt handler. If the interrupt call is to LSL.COM, a LSL initialization entry point, supported by IPXMUX.COM is returned in step 1380. The LSL initialization entry point represents an address of the protocol initialization routine into LSL.COM.

Once the address of the LSL initialization entry point is known by the IPXODI protocol, the IPXODI protocol will call that address for service. Thus, all LSL service calls are checked in step 1382 (FIG. 49) to determine if the call is a request for protocol support API entry point. If not, the multiplexer IPXMUX.COM will direct that call into LSL.COM. If so, an address of a special 2F interrupt handler (LSL Protocol Support API Handler) supported by IPXMUX.COM is returned to IPXODI.COM in step 1384.

The special interrupt handler, LSL Protocol Support API Handler, which forms a part of IPXMUX.COM, is illustrated in FIG. 50. Three services are handled by the LSL Protocol Support Handler, which is supported by the multiplexer IPXMUX.COM to set up an address for communication with a host on the network. These services are register protocol stack, bind stack and send a packet. The balance of the services are handled by LSL.COM.

The entry point of the LSL Protocol Support API Handler in IPMMUX.COM from the standpoint of IPXODI.COM is the protocol support API within the link support layer LSL. Since the link support layer LSL.COM supports various protocols, such as IPXODI and TCPIP, registration of the IPXODI.COM protocol is checked in step 1386. If the call to the link support layer LSL is to register a protocol stack, an IPXMUX register protocol stack application program interface (API) handler in step 1388 checks whether the protocol stack is IPXODI. If the protocol stack is IPXODI, the protocol stack handler sets a packet receive handler, supported by IPXMUX.COM and calls LSL.COM's protocol stack API to register the protocol. The protocol stack handler also saves the stack ID. Subsequently, in step 1390, an IPXMUX Receive Routine Linker sets the protocol stack IPXODI's receive routine address to the packet receive address supported by IPXMUX.COM.

If the protocol API call is not to register the protocol stack, the system then checks in step 1392 whether a special registration service, a bind stack service, is requested. A bind stack service, normally done before registration, is used to set up a protocol for communication, i.e. packet length, etc. If bind stack service is requested, an IPXMUX Bind Stack API handler in step 1394 is called, which forces IPXODI to bind to the wired LAN card 1352 to which IPXODI is bound before the wireless LAN card 1360 was installed in order to be compatible with the IPXODI protocol. The IPXMUX bind stack handler also saves the process ID of the binding for sending and receiving packets.

If the protocol API call is not a register protocol stack or a bind stack service, the system checks in step 1396 whether send packet service is requested. If not, the system exits and the service call is handled by LSL.COM. If so, an IPXMUX send packet routine is called in step 1398 and 1400 (FIG. 51), which sets the address of the wireless LAN card 1360 as the source node address in step 1402. The packet modifier also sets the node address of the wireless interface device 100 as the packet's destination mode address in step 1400 (FIG. 51). The send event service routine address is set to the address of the send event service routine in IPXMUX.COM before it returns.

Incoming packets are handled by an incoming packet handler illustrated in FIG. 32. In particular, incoming packets are checked in step 1404 whether the source address of the packet is from the wireless LAN card 1360. If not, the system returns. If so, the packet's source mode address is saved and set to the mode address of the wireless LAN card 1360 while the pocket destination address is set to the address of the wired LAN card 1352 to which IPOXDI is bound.

The wireless interface device 100 includes a hot icon 1408 (FIG. 37) in the hot icon area 1202 (FIG. 36) of the LCD 113C for switching control of the host computer 101 from the wireless interface device 100 and the host computer 101. While the wireless interface device 100 has control of the host computer 101, the user has the option to dim the screen of the host computer 101, as well as lock out the keyboard and mouse inputs. In particular, with reference to FIG. 37, a set-up window hot icon 1410 may be selected. Activation of the set-up window icon causes one of five selectable set-up dialog boxes to be displayed in the viewing area 1200 (FIG. 36) of the LCD 113C on the wireless interface device 100. These dialog boxes are illustrated in FIGS. 53-57, which can be selected by a graphical button bar 1412 (FIG. 53). When the "host" button is selected, a list of host computer groups that are accessible by the wireless interface device 100 as well as the specific host to which the wireless interface device 100 is connected are displayed. When the wireless interface device 100 has control of the host computer 101, the host computer screen can be dimmed and the host keyboard and mouse can be locked out by placing the pen down in the box next to those functions in the dialog box illustrated in FIG. 53. FIG. 54 relates to setting up remote keyboard macros. FIG. 55 is a maintenance dialog box which enables various maintenance functions, such as calibration of the pen, rebooting of the host, and the like. FIG. 56 relates to power settings, and in particular includes an inactivity timer for timing periods of inactivity in order to place the wireless interface device 100 in a low-power state. FIG. 57 is selectable by the screen button and enables the brightness and contrast of the LCD 113C on the wireless interface device 100 to be adjusted.

FIG. 58 illustrates a method for disconnecting the host computer 101 from the wireless interface device 100 and automatically returning control of host screen, keyboard and mouse to the host computer 101. In addition, any configuration settings of the wireless interface device, such as contrast and brightness adjustment, are also saved in order to obviate the need to readjust the wireless interface device 100, the next time it is connected.

Initially in step 1414 (FIG. 58), the system determines if the hot icon area 1202 of the LCD 113C on the wireless interface device 100 was pressed. As illustrated in FIG. 37, the hot icon area 1202 includes several hot icons. Thus, the system checks in step 1416 whether the host control mode hot icon 1408 (FIG. 37) was selected. If not, the system loops back to step 1414 and waits for the hot icon area to be pressed. If the host control mode hot icon 1408 was selected, the wireless interface device 100 sends a private message (i.e. pocket) to the host computer 101 in step 1418, requesting host control mode.

The system then checks in step 1420 whether the host computer 101 returned an acknowledgement that the private message was received. If an acknowledgement of the private message is not received by the wireless interface device 100, the attempt to enter the host control mode is aborted in step 1422. If an acknowledgement is received, the system checks in step 1424 if the mouse keyboard and mouse had been previously locked out by the wireless interface device 100 as discussed above. If so, the host keyboard and mouse are unlocked. Subsequently in step 1426, an internal flag is set indicating a request for termination of the connection with the host computer 101 in step 1428. The request for termination initiates a timer, which, when timed out, disconnects the wireless interface device 100 from the host computer 101. Thus, the system checks to determine if the host computer 101 is still connected to the wireless interface device 100 in step 1430. If so, the system determines if the request for termination has timed out in step 1432. If not, the system waits for the timer to time out and disconnects the wireless interface device 100 from the host computer 100. Once the wireless interface device 100 is disconnected, control of the host computer 101 is returned to the host computer 101.

In order to obviate the need to reconfigure the wireless interface device 100 the next time the wireless interface device 100 is connected to the host computer 101, the system checks in step 1434 whether any of the configuration data (i.e. contrast, brightness (FIG. 57) was changed. If not, the wireless interface device 100 is placed in a suspend mode in step 1436. If the configuration data did change, the new configuration data is saved in the EEPROM 111B (FIG. 12) in step 1438.

The wireless interface device 100 can determine the available hosts within range for wireless connection. The user can then select a host by way of a dialog box (FIG. 53), which will be discussed in more detail below. An important aspect of the wireless interface device 100 is that it can be connected to virtually any available hosts without any physical connections and without knowing the host address or node address beforehand, unlike known wireless and wired LAN systems where the node addresses of each of the personal computers in the network have a preassigned node address and are therefore known prior to any communications being established.

In order to initiate connection of the wireless interface device 100 to an available host 101, the set-up hot icon 1410 (FIG. 37) is selected in step 1439 (FIG. 59) which causes a set-up dialog box, as illustrated in FIG. 53 to be displayed in the viewing area 1202 (FIG. 36) of the LCD 113C. Subsequently, in step 1440, the wireless interface device 100 broadcasts network packets to be received by all available hosts 101 in range that are on the same channel and domain as the wireless interface device 100. After the network packets are broadcast, the wireless interface device 100 listens for a predetermined time period in steps 1442 and 1444 for return acknowledgement packets from the available hosts 101, which contain, among other things, the node addresses of the available hosts 101. After the time-out period the wireless interface device 100 terminates listening for responses from the available hosts 101 in step 1446. After listening is terminated, the system checks the number of responses received in step 1448. If no responses are received, the wireless interface device 100 repeats the cycle (i.e. returns to step 1440) for a predetermined number of retries as determined in step 1450.

If a response is received, the system identifies the unique node address from the responding hosts 101 in step 1452 and saves the unique host node addresses in step 1454. The list of available hosts 101 is searched in step 1456 for duplicate serial numbers. Should duplicate serial numbers be found in step 1458, a warning is generated in step 1460, warning the user that a duplicate copy of software is running on one of the responding hosts 101. In step 1462, the currently connected host is forced to appear as unavailable on the dialog box illustrated in FIG. 53.

The responding hosts 101 are sorted first by group name and then by host name in step 1464. After the sorting, an internal status list of the available hosts 101 in designated as available in step 1466. Subsequently, the available hosts and groups are displayed in the dialog box illustrated in FIG. 53 in step 1468. Movement of the cursor (by a pen-down event) to the desired host 101 selects that host 101. A "connect" button on the dialog box is then selected to connect the wireless interface device 100 to the selected host 101.

FIGS. 60 and 61 relate to remote keyboard macros on the wireless interface device 100. An important aspect of the wireless interface device 100 is that the remote keyboard macros are provided by way of a wireless connection. FIG. 60 relates to developing the macros while FIG. 61 is directed to using the macro.

Referring to FIG. 37, the wireless interface device 100 includes two user-defined hot icons 1472 and 1474, located in the hot icon area 1202 (FIG. 36) of the LCD 113C, that can be used for the macros. These hot icons 1472 and 1474 are configurable in a set-up mode, which, as discussed above, is under the control of the set-up hot icon 1410 (FIG. 37). Once the set-up hot icon 1410 is selected, a hot key button 1470 on the dialog box illustrated in FIG. 54 is selected. As noted in FIG. 54, the dialog box includes two configurable macros. These macros are configured by way of the two edit fields 1472 and 1474 (FIG. 54). In order to configure the macros, the icon for the desired edit field 1472 or 1474 is selected. These edit fields 1472 and 1474 are configurable by way of a virtual on-screen keyboard (OSK), selectable by way of a hot icon 1480 (FIG. 37).

Referring to FIG. 60, the system checks in step 1476 whether there has been a pen-down event in the viewing area 1202 (FIG. 36) of the LCD 113C and, in step 1478, whether the OSK hot icon 1480 (FIG. 37) was selected. If not, the system loops back to step 1476. If so, the selected key on the OSK is translated into a keyboard scan code in step 1480 and a visual indication of the key selected in the edit field 1472 or 1474 in step 1482. The process is repeated until the macro (i.e. WIN, DIR), followed by a carriage return 1486, is complete and the macro is saved in the EEPROM 111B (FIG. 12) in step 1484. A clear button 1486 is provided in the dialog box illustrated in FIG. 54 for each edit field 1472 and 1474. These clear buttons 1486 enable the edit fields to be cleared in the EEPROM 111B (FIG. 12).

Activation of the remote keyboard macros is accomplished by pressing down on the user-defined hot icons 1472 or 1474, located in the hot icon area 1202 (FIG. 36) of the LCD 113C. The system checks in steps 1486 and 1488, whether the user defined hot icons 1472 or 1474 are selected. If the user-defined hot icons 1472 or 1474 are not selected, the system returns to step 1486. Once one of the user-defined hot icons 1472 or 1474 is selected, the keyboard scan code sequence, stored in the EEPROM 111B (FIG. 12), is retrieved for the selected hot icon 1472 or 1474 in step 1490, which are then individually transmitted to the host 101 in step 1492. These scan codes are then written to the keyboard buffer on the host 101 in step 1494. Subsequently, in step 1496, the host 101 processes the scan codes as though they originated from the host keyboard.

As mentioned above, the wireless interface device 100 includes several flash memory devices 742-748 (FIG. 25). The flash memory device 742 includes a protected area which contains the system BIOS, and a sufficient amount of functionality to enable the wireless interface device 100 to be rebooted to enable reprogramming of the flash memory devices 742-748 by way of the serial port 788 (FIG. 23) in the event of a flash disaster.

In order to upgrade the flash memory devices 742-748, the upgrade disks are installed in an available host computer 101. In particular, the flash upgrade software is written to a predetermined directory on the host's 101 hard disk. After the flash upgrade disks are installed, the wireless interface device 100 is turned on in step 1498 (FIG. 62) by way of the main power switch 855 (FIG. 28). Subsequently, in step 1500, a connection between the host computer 101 and wireless interface device 100 is initiated in step 1500 by first selecting the configuration hot icon 1410 (FIG. 37).

Subsequently, the maintenance button on the dialog box is selected to get to the dialog box illustrated in FIG. 55. An upgrade button 1502 on the dialog box illustrated in FIG. 55 is selected in step 1504. In order to prevent programming errors, the radio quality is checked in step 1506 before proceeding. If the radio quality is poor, the upgrade is aborted. If the radio quality is adequate, power management is disabled in step 1508 to prevent the wireless interface device 100 from going into a reduced power state as discussed above during programming of the flash memory devices 742-748. After the power management is disabled, a portion of the DRAM memory 111A (FIGS. 18 and 24) in the wireless interface device 100 is set aside to receive a flash sector from the host computer 101 in step 1510. Subsequently, the wireless interface device 100 polls the host computer 101 to determine the correct numbers of sectors in the flash update and whether the sectors are available on the hard disk of the host computer 101 in steps 1512 and 1514. If the flash update files are not on the host hard drive or an incorrect number of sectors are available on the host hard disk, the update is aborted. Otherwise, the system requests the path/file data from the host computer 101 in step 1516. Subsequently, each sector (file) in the flash update is read by the host computer 101 and uploaded over the radio to the DRAM 111A in the wireless interface device 100 in step 1518. After the sectors are written to the DRAM 111A in the wireless interface device 100, a BIOS call is made to write the sectors in the DRAM 111A to the flash memory devices 742-748 in step 1520.

In step 1522 the system checks for errors in writing to the flash memory devices 742-748. Should any errors be detected, the update is aborted. If no errors are detected, the system checks in step 1524 whether all of the sectors from the DRAM 111A have been written to the flash memory devices 742-748 in the wireless interface device 100. If not, the system loops back to step 1516. Once all of the files have been transferred to the flash memory devices 742-748, the wireless interface device 100 is rebooted in step 1526. Once the wireless interface device is rebooted, the system will be able to utilize the updated software in the flash memory devices 742-748.

FIG. 63 illustrates the routine for writing the flash update sectors from the DRAM 111A to the flash memory devices 742-748. Since the flash updates are stored in the DRAM memory 111A, the programming is aborted if the AC power is turned off as determined in step 1528 since the flash update data in the DRAM 111A will be lost when the battery is exhausted. In order to prevent errors during programming, interrupts, as well as the power management, are disabled on the wireless interface device 100 in steps 1530 and 1532. After the interrupts and the power management are disabled, the flash memory device is erased in step 1534. If errors occur during erasure, as determined in step 1536, updating of the particular flash memory device 742-748 is aborted. If not, a sector from the DRAM 111A is written to the flash memory devices 742-748 in step 1538. After the sector is written to the flash memory devices 742-748, the system checks in step 1540 whether any errors occurred. If so, the update is aborted. If not, the interrupts, as well as the power management, are enabled in step 1542 when all sectors have been reflashed.

As mentioned above, the wireless interface device 100 can be connected to any of the available hosts 101 that appear in the dialog box illustrated in FIG. 53 in the manner described above. The system illustrated in FIGS. 64A and 64B obviates the need for the user to select a host 101 for connection each time the wireless interface device 100 is powered up, by automatically connecting the wireless interface device 100 to the last host 101 to which it was successfully connected. As will be discussed in more detail below, when a host 101 is selected from the dialog box illustrated in FIG. 53 for connection to the wireless interface device 100 and a connection is successfully achieved, the node address of that host 101 is stored in the EEPROM 111B (FIG. 12). Subsequently, once the wireless interface device 100 is powered up in step 1544, the system reads the node address from the EEPROM 111B, and reads it to a specific location in DRAM 111A (FIGS. 18 and 24) in step 1546. After the node address is written to the DRAM 111A, the system checks the node address to determine whether it is valid in step 1548. Invalid node addresses occur anytime the wireless interface device 100 makes an attempt to connect to a host 101, which fails during automatic reconnecting or is later disconnected by the end user. Thus, if a successful connection is not made or if there is a manual disconnection, the node address is cleared from the DRAM 111A in step 1550 and thus will be invalid. Subsequently, if the automatic reconnect fails in order to facilitate connection of the wireless interface device 100 to another available host 101, the set-up dialog box illustrated in FIG. 53 is displayed on the display 113C of the wireless interface device 100 in step 1552. After the host selection set-up dialog box is displayed on the wireless interface device 100, the system checks in step 1554 whether the wireless interface device 100 is connected to an available host 101. Normally, if an invalid address is found in step 1548 and the host selection set-up dialog box appears on the display 113C of the wireless interface device 100, there will be no connection to an available host 101 and the system will jump to step 1556, where it checks if the hot icon area 1202 (FIG. 37) has been depressed. Normally in this situation, since the host selection dialog box is already being displayed on the screen 113C of the wireless interface device 100, the only hot icon that can affect the situation is a sleep-face hot icon 1558 (FIG. 37), which places the wireless interface device 100 in a low-power sleep mode. In a normal situation when the wireless interface device 100 is first powered up, the sleep-faced hot icon 1558 is not depressed and the system waits for the user to select an available host 101 from the host set-up dialog box illustrated in FIG. 53 as discussed above in step 1560. Once an available host 101 is selected, the system loops back to step 1562 and attempts to establish connection with the selected host 101.

In step 1564 the system checks whether or not the connection was successful. If not, the system goes to step 1550 and clears the node address for the selected host 101 from the DRAM 111A and displays the host selection set-up dialog box in step 1552. If the connection between the wireless interface device 100 and the host 101 is successful, the node address of the host 101 is saved in a specific DRAM location in step 1566, and in turn, written to the EEPROM 111B (FIG. 12) in step 1568. After the node address of the selected host 101 is stored in EEPROM 111B, the wireless interface device 100 will display whatever is being displayed on the host 101 in step 1570.

After a connection is established between the host 101 and the wireless interface device 100, the system continuously checks for hot icons being selected in step 1572. If no hot icons are selected, the system will loop back and continue to check for the selection of a hot icon. If the system determines that a hot icon is selected, the system checks in step 1574 whether the set-up dialog hot icon 1410 (FIG. 37) was selected. If so, the system loops back to step 1552 and displays the host selection set-up dialog box illustrated in FIG. 53 on the display 113C of the wireless interface device 100. If the set-up dialog hot icon 1410 is not selected, the system checks in step 1576 whether the sleep-face hot icon 1558 is selected in step 1576. If not, the system checks in step 1578 whether other hot icons in the hot icon area 1202 (FIG. 36) were selected and the appropriate action is taken. The system then goes to step 1570 and, in turn, and continually checks for the selection of other hot icons in step 1572.

If it is determined in step 1576 that the sleep-face hot icon 1410 is selected, the system checks in step 1580 whether a double pen-down event occurred at the location of the sleep-face hot icon 1410. As mentioned above, the sleep-face hot icon 1410 causes the wireless interface device 100 to go into a low-power mode. However, before placing the wireless interface device 100 in a low-power mode, the node address of the host 101 to which the wireless interface device 100 is connected is saved in a specific location of the DRAM 111A and, in turn, written to the EEPROM 111B in step 1582. After the node address is saved, the wireless interface device 100 is powered down in step 1584.

The system discussed above is thus able to automatically connect the wireless interface device 100 to the last host 101 to which it was connected. After the automatic reconnect, should the set-up window hot icon 1410 (FIG. 37) be selected, the host selection set-up dialog box illustrated in FIG. 53 will be displayed on the screen 113C of the wireless interface device 100. Subsequently, the system will go to step 1554 and check whether the wireless interface device 100 is connected to a host 101. In this case, since the wireless interface device 100 will still be connected to the available host, the system then checks in step 1586 whether a disconnect button on the host selection dialog box illustrated in FIG. 53 has been depressed. If not, the system goes to step 1556 and continuously waits for a hot icon in the hot icon area 1202 (FIG. 36) of the LCD 113C to be depressed. If the disconnect button in the host selection set-up dialog box illustrated in FIG. 53 is depressed, the node address for the host 101 to which the wireless interface device 100 is connected is erased from the specific location in the DRAM 111B in step 1588. Subsequently, the system goes to step 1556 and waits for a hot icon in the hot icon area 1202 (FIG. 37) to be depressed.

As mentioned above, the wireless interface device 100 includes a virtual on-screen keyboard (OSK), as illustrated in FIG. 66. More particularly, the OSK is configurable by the buttons 1590, 1592, 1594 and 1596 in a control box located at the top of the OSK. These buttons 1590, 1592, 1594 and 1596 enable the OSK to be configured. For example, a button 1590 displays the OSK as illustrated in FIG. 66A with a full keyboard and numeric keypad. The button 1592 is a toggle which displays the keyboard without the numeric keyboard as illustrated in FIG. 66B. The button 1594 displays the numeric keypad with the NUM LOCK off as illustrated in FIG. 66C, or alternatively displays the OSK as a numeric keyboard NUM LOCK on as illustrated in FIG. 66D. The button 1596 allows the size of the OSK to be varied. The "X" button closes the window displaying the OSK.

As mentioned above, the display 113C on the wireless interface device 100 displays whatever is being displayed on the host 101 when a connection is made. Since the graphics for the OSK is generated locally at the wireless interface device 100, a remote occlusion region is generated at the host 101 to prevent the host 101 from painting over the OSK on the display 113C of the wireless interface device 100. The remote occlusion region is analogous to a window in the display of the host 101 in which the host 101 is prevented from using.

Referring to FIG. 65A, the system monitors the hot icon area 1202 (FIG. 36) to determine if any of the hot icons have been pressed. As discussed above, the system includes an OSK hot icon 1480 (FIG. 37), which displays the OSK on the LCD 113C of the wireless interface device 100 when depressed. If the system determines in step 1598 that a hot icon has been depressed, it checks in step 1600 whether the OSK hot icon 1480 was pressed. If not, the system loops back to 1598 and continually checks for hot icons being pressed. If the OSK hot icon 1480 has been depressed, the system determines the last configuration for the OSK in step 1602 (i.e. FIGS. 66A-66D). Once the configuration of the last OSK is determined in step 1602, the system then checks the operating system and video mode of the host 101 in step 1604. Depending on whether the host 101 is in text or graphics mode will determine whether the OSK image on the wireless interface device 100 is merely shadowed onto the display of the host 101 by way of a private message, as will be discussed in more detail below, or whether the remote occlusion region at the host 101 is established by drivers in the host software, which create the remote occlusion region by way of ASCII characters. Thus, in step 1606, if the system determines that the host 101 is in the text mode, an occlusion region on the display of the host 101 is created using the host control drivers in step 1608. In step 1610, the system checks whether the occlusion region was successfully established. If not, the system then checks in step 1612 whether the OSK is currently visible on the display 113C of the wireless interface device 100. If not, the display of the OSK is aborted in step 1614. If it is determined in step 1612 that the OSK is currently visible on the LCD 113C of the wireless interface device 100, any reconfiguration of the OSK is ignored and the configuration of the last OSK is continuously displayed in step 1614. If it is determined in step 1610 that the remote occlusion region is successfully established, the system goes to step 1616, which enables the OSK to be used.

If it is determined in step 1606 that the host 101 is not in a text mode, the system checks in step 1618 whether the host 101 is in a graphics mode. If not, the system goes to step 1620 and sets the video mode to VGA graphics in the wireless interface device 100 and subsequently proceeds to step 1608 to establish the occlusion region in the host 101 by host control drivers. If the host is in a graphics mode, the system next checks in step 1622 whether the host 101 is running a Windows application. If not, the system returns to step 1608 and establishes the occlusion region on the display of the host 101 using the host control drivers.

If it is determined in step 1622 that the host 101 is running a Windows application, the occlusion region on the host 101 is established by way of a private message sent by the wireless interface device 100 to the host 101 in step 1624. After the private message is sent, the system checks in step 1626 to determine if it was successfully sent. If not, the system proceeds to step 1612 and checks to determine if an OSK is currently visible. If the private message is successfully sent, the system checks in step 1628 whether the private message was successfully received by the host 101. If so, the system goes to step 1630 and checks whether the private message was acknowledged by the host 101. If so, the system goes to step 1616 and draws the OSK at the user-requested coordinates. If not, the system goes to 1612. If it is determined in step 1628 that the private message has not been received, the system continually checks for receipt of the private message for a predetermined time-out period in step 1632. Should a time-out occur before the private message is acknowledged by the host 101, the system again will go to step 1612.

The OSK includes a control bar 1632 (FIG. 66A). The control bar 1632 enables the location of the OSK on the LCD 113C of the wireless interface device 100 to be changed by touching the control bar 1632 with the pen and dragging it to the desired location on the LCD 113C of the wireless interface device 100. Anytime the user changes the location of the OSK on the LCD 113C of the wireless interface device 100 as acknowledged by the system in step 1634, the system then returns to step 1604 to determine the video mode of the host computer 101. As discussed above, the video mode determines whether the remote occlusion region on the display of the host 100 is created by shadowing the OSK on the display of the host by way of the private message or whether the occlusion region on the display of the host is created by local drivers using ASCII characters. The system then goes to step 1606.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described above.