Communication on non-continuously sampled lines

[0002] This invention relates generally to communicating data. More particularly, this invention relates to communicating data on signals that are normally static, such as configuration jumper signals.

[0003] Many electronic devices have a communication channel that is used for development, diagnostic, and production functions. For example, a disk drive may have an RS-232 interface connected through a DB-9 connector so that a firmware developer can monitor the internal state and functioning of the disk drive. This same interface may also be used later in a production environment to initiate and monitor a final self-test sequence before packaging and shipping the device to a consumer. Unfortunately, a large connector, such as a DB-9 or DB-25, is unsightly, adds cost, and may be difficult to find room for on the product. Furthermore, it may be desirable to discourage the end user from accessing this interface. The connector can be hidden, and access prevented by placing the connector underneath the case, or skin, of the product. However, if the connector is hidden in this way, it is inaccessible when the product is completely assembled. This makes it impossible to access the communication product after a certain stage of manufacture, and impossible to access when the product is being used in it's intended manner.

[0004] Accordingly, there is a need in the art for a communication channel that can function after a product is entirely assembled, but does not advertise its presence. It is desirable that this channel not necessarily require an additional connector. Such a channel should also be capable of communicating both serial and parallel data in both directions. Finally, such a channel should be capable of implementation using existing features that are accessible from the outside of a filly assembled device.

[0005] The invention provides a communication channel that is accessible when the product is entirely assembled, but appears to be, and functions like, configuration jumpers to the end user. This communication channel requires only a small number of additional parts, and possibly even saves money by eliminating the need for a large, expensive connector on each device. The invention is readily adaptable to a variety of interfaces, both standard and non-standard.

[0006] An embodiment of a communication channel according to the invention utilizes the terminals of a configuration jumper block as communication paths to an interface device. The terminals of the configuration jumper block may be wired differently depending on the desired function (i.e. send data, receive data, etc.) of the terminals. The configuration information needed by the device is read from the terminals of the configuration block when the communication channel is not active. Switches on the interface device are used to set the configuration information.

[0007] FIG. 1 is a schematic illustration of a communication path that can send and receive data to and from an interface device and a host device using a non-continuously sampled signal.

[0008] FIG. 2 is a schematic illustration of a communication path that can send data from an interface device to a host device using a non-continuously sampled signal.

[0009] FIG. 3 is a schematic illustration of a communication path that sets a non-continuously sampled signal either by jumper, or by switch on an interface device.

[0010] Many electronic devices have signals that are sampled only once, or at most a few times during the devices normal operation. These are non-continuously sampled signals. Examples of this type of signal are signals set by a configuration jumper. These jumpers may set some internal configuration information, such as the device address or interrupt number, by determining that state of a set of signals when they are read during a power-up sequence.

[0011] FIG. 1 is a schematic illustration of a communication path that can send and receive data to and from an interface device and a host device using a non-continuously sampled signal. In FIG. 1, signal J1 is a non-continuously sampled signal. The elements inside box 102 are on the host device. In FIG. 1 terminal 122 of connector 104 is coupled to a positive supply voltage. The other terminal of connector 104, terminal 124, connects to one terminal of resistor 108 and one terminal of resistor 106. The other terminals of resistors 108 and 106 are connected to J1 and a negative supply, respectively. In the preferred embodiment, resistor 108 is 1 KΩ and resistor 106 is 50 KΩ. During normal operation of the host device, jumper 112 may optionally connect the two terminals of connector 104. If jumper 112 is not in place, signal J1 is pulled down through resistors 108 and 106. If jumper 112 is in place, terminal 124 is connected through jumper 112 to a positive supply voltage. This pulls signal J1 high through resistor 108. Resistor 106 prevents the positive supply from being shorted to the negative supply when jumper 112 is in place.

[0012] For the host to send data to an interface device, jumper 112, if present, is removed. Connector 110 is then interfaced with connector 104 so that terminal 126 of connector 110 connects to terminal 122 and terminal 128 of connector 110 connects to terminal 124. These connections are shown by dotted lines 116 and 114, respectively. Connection 116 is optional but may be used to provide a positive supply voltage to the interface device. Connector 110, resistor 120, and switch S1118 are either on or connected to the interface device even when the interface device is not connected to the host device. One terminal of single-pole single-throw switch S1118 is connected to a positive supply voltage. The other terminal of switch S1118 is connected to a first terminal of resistor 120. A second terminal of resistor 120 is connected to terminal 128 of connector 110. This node is the DATA node. In the preferred embodiment, resistor 120 is 10 KΩ. When

[0013] The DATA node may be connected to an RS-232 interface device, a Universal Asynchronous/Synchronous Receiver Transmitter (USART), parallel interface port, or some other input/output device to receive or send data sent to and from the host device on signal J1. In the preferred embodiment, the DATA node is connected to an RS-232 interface device.

[0014] With connector 110 in place, the position of switch S1118 sets the value of signal J1 when signal J1 is sampled. After J1 has been sampled, the host device may send data by overdriving the relatively high impedances of resistor 120 and 106 with a driver or buffer in series with the relatively low impedance of resistor 106. A device on the interface device may send data to the host by overdriving resistor 120 and 106 with a driver or buffer connected to the DATA node.

[0015] In FIG. 1, terminal 122 is coupled to a positive supply voltage and resistor 106 is connected to a negative supply voltage. Alternatively, one of ordinary skill in the art would recognize that if terminal 122 were coupled to a negative supply voltage, and resistor 106 were connected to a positive supply voltage, then when jumper 112 was not in place, signal J1 would be pulled high and when jumper 112 was in place, J1 would be pulled low. Switch S1118 could then be connected to a negative supply voltage instead of a positive supply voltage to set the value of signal J1 when signal J1 is sampled.

[0016] FIG. 2 is a schematic illustration of a communication path that can send data from an interface device to a host device using a non-continuously sampled signal. In FIG. 2, signal J2 is a non-continuously sampled signal. The elements inside box 202 are on the host device. In FIG. 2 terminal 222 of connector 204 is coupled to a positive supply voltage through resistor 208. Terminal 222 is the RXD node of the host device. The other terminal of connector 204, terminal 224, is connected to signal J2, which also connects to one terminal of resistor 206. The other terminal of resistor 206 is connected to a negative supply voltage. In the preferred embodiment, resistor 208 is 10 KΩ and resistor 206 is 50 KΩ. During normal operation of the host device, jumper 212 may optionally connect the two terminals of connector 204. If jumper 212 is not in place, signal J2 is pulled down through resistor 206. If jumper 212 is in place, terminal 224 is pulled up through jumper 212 and resistor 208 to a positive supply voltage. This pulls signal J2 high. Resistor 206 prevents the positive supply from being shorted to the negative supply when jumper 212 is in place.

[0017] For the interface device to send data to host, jumper 212, if present, is removed. Connector 210 is then interfaced with connector 204 so that terminal 226 of connector 210 connects to terminal 222 and terminal 228 of connector 210 connects to terminal 224. These connections are shown by dotted lines 216 and 214, respectively. Connector 210 and switch S2220 either are on or connected to the interface device even when the interface device is not connected to the host device. One terminal of single-pole single-throw switch S2220 is connected to terminal 226 which is the TRANSMIT DATA node. The other terminal of switch S2220 is connected to terminal 228. Data is placed by the interface device on signal TRANSMIT DATA and is received by the host device on node RXD.

[0018] The TRANSMIT DATA node may be connected to an RS-232 interface device, a Universal Asynchronous/Synchronous Receiver Transmitter (USART), parallel interface port, or some other input/output device to send data sent to the host device. In the preferred embodiment, the TRANSMIT DATA node is connected to an RS-232 interface device.

[0019] With connector 210 in place, the position of switch S2220 sets the value of signal J2 when signal J2 is sampled. To function properly, the TRANSMIT DATA node should be held high until J2 has been sampled. In the preferred embodiment, this is easily accomplished since the idle state of an RS-232 line is defined to be high. After J2 has been sampled, the interface device may send data by overdriving the relatively high impedances of resistors 208 and 206 with a driver or buffer.

[0020] In FIG. 2, terminal 222 is coupled to a positive supply voltage through resistor 208 and resistor 206 is connected to a negative supply voltage. Alternatively, one of ordinary skill in the art would recognize that if terminal 222 were coupled to a negative supply voltage, and resistor 206 were connected to a positive supply voltage, then when jumper 212 was not in place, signal J2 would be pulled high and when jumper 212 was in place, J2 would be pulled low. The TRANSMIT DATA node would then need to be held low until after the sampling of J2.

[0021] FIG. 3 is a schematic illustration of a communication path that sets a non-continuously sampled signal either by jumper, or by switch on an interface device. In FIG. 3, signal J3 is a non-continuously sampled signal. The elements inside box 302 are on the host device. In FIG. 3 terminal 322 of connector 304 is coupled to a negative supply voltage. The other terminal of connector 304, terminal 324, is connected to signal J3, which also connects to one terminal of resistor 306. The other terminal of resistor 306 is connected to a positive supply voltage. In the preferred embodiment, resistor 306 is 10 KΩ. During normal operation of the host device, jumper 312 may optionally connect the two terminals of connector 304. If jumper 312 is not in place, signal J3 is pulled up through resistor 206. If jumper 312 is in place, terminal 324 is pulled down through jumper 312 by a negative supply voltage. This pulls signal J3 low. Resistor 306 prevents the positive supply from being shorted to the negative supply when jumper 312 is in place.

[0022] For the interface device to set the value of J3, jumper 312, if present, is removed. Connector 310 is then interfaced with connector 304 so that terminal 326 of connector 310 connects to terminal 322 and terminal 328 of connector 310 connects to terminal 324. These connections are shown by dotted lines 316 and 314, respectively. Connection 316 is optional, but may be used to establish a common reference level, or provide a negative supply voltage to the interface device. Connector 310 and switch S3320 either are on or connected to the interface device even when the interface device is not connected to the host device. One terminal of single-pole single-throw switch S3320 is connected to terminal 328, which is also the J3 signal node. The other terminal of switch S3320 is connected to a negative supply. With connector 310 in place, the position of switch S3320 sets the value of signal J3 when signal J3 is sampled.

[0023] In FIG. 3, terminal 322 is coupled to a negative supply voltage. Alternatively, one of ordinary skill in the art would recognize that if terminal 322 were coupled to a positive supply voltage, and resistor 306 were connected to a negative supply voltage, then when jumper 312 was not in place, signal J3 would be pulled low and when jumper 312 was in place, J3 would be pulled high.

[0024] In the preferred embodiment, the host device has an AT Attachment Packet Interface (ATAPI) channel as one interface to a host computer. Many devices that have ATAPI channel have configuration jumpers to set the ATAPI Master, Slave, and Cable Select configuration. In the preferred embodiment, these configuration jumpers are sampled only on power up and are used with the communication paths described in FIGS. 1, 2, and 3 to provide a bi-directional RS-232 communication channel between the host device and an interface device. This secondary RS-232 link may be used for development, diagnostic, and production functions without requiring the skin of the host device be removed to access a special connector. In the preferred embodiment, the Master configuration jumper terminals are used to send data from the host device to the interface device. This is done using the circuitry and communication path shown in FIG. 1. The Slave configuration jumper terminals are used to send data from the interface device to the host device. This is done using the circuitry and communication path shown in FIG. 2. The Cable Select configuration jumper terminals are set by a switch on the interface device using the circuitry and communication path shown in FIG. 3.

[0025] Although several specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. The invention is limited only by the claims.