Apparatus and Method for Detecting Insertions and Removals of Floppy Disks by Monitoring Write-Protect Signal

The present invention relates to the field of computer systems and, more particularly, to a method and system for determining insertions and removals of floppy disks in a floppy disk drive.

In personal computer systems, floppy disks provide an inexpensive and easily portable storage medium. In brief, floppy disks allow a user of a computer system to store and recall data (e.g., application programs and associated files) as needed. When the user desires to store or recall a particular piece of data to/from a floppy disk, the user simply inserts the desired disk into a floppy disk drive of a personal computer system and invokes an appropriate command from an application program (e.g., save file or open file command). As floppy disks are frequently swapped in and out of the floppy disk drive, it is desirable to provide a method and system that can notify application programs when floppy disks are removed from the floppy disk drive and when floppy disks are inserted in the floppy disk drive.

Effectuating prompt notification of such insertions and removals is difficult in machines that do not provide hardware support for determining insertions and removals of floppy disks. For example, machines adhering to the "IBM" standard architecture do not provide hardware support for determining insertions and removals of floppy disks. Instead, these machines provide only a signal known as a changeline. This changeline is activated by an opening of the floppy disk drive's door and is reset by powering the floppy disk drive's motor and repositioning the floppy disk drive's heads on the floppy disk. The practical use of this changeline is limited as an activated changeline does not indicate whether the floppy disk drive contains a floppy disk but instead only indicates whether the floppy drive's door has been opened since the last resetting of the changeline.

Conventional systems determine whether an activated changeline indicates an insertion or a removal of a floppy disk by attempting to reset the changeline. As a changeline can be reset only when a floppy disk is present in the floppy disk drive, conventional systems distinguish between floppy disk insertions and removals by monitoring the changeline to determine whether the reset attempt has been successful (i.e., to determine whether the resetting attempt returned the changeline to an inactive state). For example, if an attempt to reset an activated changeline is not successful, conventional systems determine that the activated changeline represents a floppy disk removal. Similarly, if an attempt to reset an activated changeline is successful, conventional systems determine that the activated changeline represents an insertion of a floppy disk, or, more particularly, a removal and an insertion of a floppy disk. Attempting to discern the meaning of an activated changeline by attempting to reset the changeline is flawed because this technique (1) requires powering the floppy drive's motor for an extended period of time, (2) requires repositioning the floppy disk drive's heads, and (3) causes the floppy disk drive's light (hereafter LED) to become illuminated. Each of these three aspects require extended powering of the floppy disk drive's components. Such extended powering is undesirable for three reasons. First, the extended powering drains a substantial amount of power from the computer system. This draining of power complicates power management timing strategies. The phrase "power management strategies" refers to a concept of allocating power between differing components of the computer system. In brief, power is allocated by dividing the use a total amount of power between the differing components of the computer system. The total amount of power available to a computer system at any one time is relatively constant as the computer system uses a constant voltage as its power source (e.g., a DC voltage). Consequently, when the power usage for one component increases, the remaining amount of power available to the other components and the complexity of the timing strategies is increase. The time and effort required to create and debug the timing strategies is directly proportional to their complexity. Accordingly, this complexity should be minimized whenever possible. Second, the extended powering represents an inefficient use of energy. This problem is particularly acute for battery-powered computer systems. For these types of systems, such extended powering quickly drains the computer system's battery and temporarily renders the system unusable. Third, the extended powering leads to premature fatigue of the floppy disk drive's components (e.g., the floppy disk drive's motor). For these masons, the conventional technique for determining insertions and removals of floppy disks is inadequate.

The present invention is directed towards a facility for determining insertions and removals of floppy disks in a floppy disk drive. The facility, relative to conventional systems, helps to increase lifetimes of floppy disk drive components and simplifies a computer system's power management timing strategies. By evaluating states of a write protect signal, the facility detects when floppy disks of a predetermined type (e.g., a write protected type or a non-write protected type) are inserted into, and removed from, the floppy disk drive. More specifically, the facility determines such insertions and removals by evaluating a current state of the write protect signal in light of a default state of the write protect signal. For example, a first embodiment of the facility (1) determines whether the write protect signal's default state (i.e., the state of the write protect signal when disk drive is empty) indicates a write protect status or a non-write protect status, and (2)evaluates a current write protect signal's state to determine whether the floppy disk drive contains a floppy disk of the predetermined type. By monitoring the write protect signal for state changes, the first preferred embodiment can detect insertions and removals of disks of the predetermined type. In a second embodiment, the facility compares current and default states of the write protect signal to determine whether an activated changeline indicates an insertion or a removal of a floppy disk of the predetermined type.

The present invention is exceptionally useful for types of applications where prompt notification of floppy disk insertions and removals is particularly desirable. An autorun program (a program that is executed automatically upon detection) is an example of a type of application where prompt notification of insertions and removals is particularly pertinent. The desirability of prompt notification is acute during the developmental stage of the autorun program (e.g., the stage in which a software developer is debugging the autorun program). In this stage, the software developer is continuously updating and improving the autorun program. To test each updated and improved version of the autorun program, the developer inserts a floppy disk containing the autorun program into the floppy disk drive. Upon recognizing that the inserted floppy disk contains an autorun file, the operating system directs the central processing unit to execute the autorun file. The operation of Autorun Programs is described in more detail in the previously incorporated co-pending application entitled "Method and System for Automatically Running a Program." When prompt notification of the floppy disk insertion is not effectuated, the software developer is forced to manually inform the operating system that a floppy disk has been inserted (e.g., by directing the operating system to inspect the contents of the floppy disk drive). Manually informing the operating system of floppy disk insertions is inefficient and is frustrating for the software developer. Another example of a type of application where prompt notification of floppy disk insertions and removals is particularly pertinent is a file management application (e.g., "WINDOWS EXPLORER" by Microsoft Corporation, Redmond, Wash.). These types of applications maintain directories that list the files which are currently contained on a particular drive (e.g., the files of the floppy disk that is currently present in the floppy disk drive). For such application programs, prompt notification of floppy disk insertions and removals is essential to the proper maintenance of these drive directories. Accordingly, the present invention is markedly beneficial for use in computer systems using these two types of applications.

FIG. 1 is a diagram illustrating states of a changeline signal and a write protect signal as they are evaluated in a preferred embodiment of the present invention.

FIG. 2 illustrates a personal computer for practicing the preferred embodiment of the present invention.

FIG. 3 is a flow diagram of the steps for determining floppy disk insertions and removals in the preferred embodiment of the present invention.

FIG. 4 is a flow diagram of the steps for determining the write protect signal's logic in the embodiment of the present invention.

FIG. 5 is a flow diagram of the steps for evaluating changeline and write protect signals in the preferred embodiment of the present invention.

A preferred embodiment of the present invention is directed towards a facility for determining insertions and removals of floppy disks in a floppy disk drive. The facility utilizes a write protect signal to determine whether an activated changeline represents an insertion or a removal of a floppy disk. Utilizing the write protect signal as an aid in determining insertions and removals of floppy disks in the floppy disk drive represents a significant departure from techniques employed in conventional systems. More specifically, utilization of such a signal enables the present invention to evaluate the meaning of an activated changeline without (1) powering up the drive motor for extended periods of time, (2) repositioning the floppy drive's heads, or (3) illuminating the floppy disk drive's LED. As a result, the facility, relative to conventional systems, helps to increase floppy disk drive motor lifetimes and simplifies the computer system's power management timing strategies.

As mentioned above, the facility evaluates a write protect signal to determine whether an activated changeline represents an insertion or a removal of a floppy disk in the floppy disk drive. This write protect signal is provided in all machines that adhere to the "IBM" standard architecture. The write protect signal identifies whether a floppy disk contained in the floppy disk drive is or is not write protected. The floppy disk drive determines a floppy disk's write protect status by evaluating whether a notch (or a hole) in the disk's casing is or is not exposed. As the name implies, a non-write protected disk allows the user to read data from the disk and to write data onto the disk. Analogously, a write protected floppy disk allows the user to read data from the disk but prohibits the user from writing data onto the disk. When a disk is not contained in the floppy disk drive, the write protect signal defaults to a constant state (hereinafter "default state"). Depending on the manufacturer and model of particular floppy disk drives, this default state may indicate a write protect status or a non-write protect status. By (1) determining whether the write protect signal's default state indicates a write protect status or a non-write protect status, and (2) evaluating a current write protect signal's state upon observing an activated changeline, the facility determines whether the activated changeline represents an insertion or a removal of a floppy disk. As will be made apparent from the discussion below, when the write protect signal's default state indicates a write protect status, the present invention can detect insertions and removals of non-write protected floppy disks. Similarly, when the write protect signal's default state indicates a non-write protect status, the present invention can detect insertions and removals of write protected floppy disks. In summary, the present invention can detect insertions and removals of "non-default" types of floppy disks, where "non-default" refers to the type (i.e., write protected or non-write protected) of floppy disk that is not indicated by the default state of the write protect signal.

FIG. 1 is a diagram illustrating states of a changeline signal and a write protect signal. This diagram illustrates how the facility evaluates the states of these two signals to determine insertions and removals of disks of a non-default type. Assuming that a floppy disk is not present in the floppy disk drive on power-up, the write protect signal will be in its default state and the changeline signal will be in its active state (reference A). Upon insertion of a disk of the non-default type, the write protect signal is placed in a non-default state (reference B). However, the changeline remains in the active state as the changeline cannot detect the insertions of floppy disks. When the floppy disk is accessed, or an explicit attempt to reset the changeline is made, the changeline is placed in its inactive state (reference C). As soon as the disk is removed from the floppy disk drive, the changeline is placed in its active state and the write protect signal is placed in its default state (reference D). When a second disk of the non-default type is inserted into the floppy disk drive, the write protect signal is returned to its non-default state while the changeline remains in its active state (reference E). When this second disk is accessed, the changeline returns to its inactive state (reference F). These state changes are summarized below in Tables 1 and 2. Each table illustrates cases where the changeline utilizes a high-logic state (i.e., "T") to indicate an activated changeline. However, those skilled in the art will appreciate that the present invention is equally applicable to changelines that use a low-logic state (i.e., "0") to indicate an activated changeline. Table 1 illustrates the case where the write protect signal defaults to a write protect status where a high-logic state indicates write protect. Table 2 illustrates the case where the write protect signal defaults to a non-write protect status where a low-logic state indicates non-write protect.

Having described the functionality of changeline signals and write protect signals, the utilization of these signals in a preferred embodiment of the present invention will now be described in detail.

FIG. 2 illustrates a personal computer system for practicing the preferred embodiment of the present invention. This computer system features a central processing unit 210, a memory area 220, an input device 230, a floppy disk controller 240, a floppy disk drive 250, a video display 260, and a system clock 290. These components are interconnected as shown. The main memory area 220 contains a floppy disk driver 270, an operating system 275, and an application program 280. The processing steps explained below with reference to FIGS. 3-6 are performed by the floppy disk driver 270. However, those skilled in the art will appreciate that these processing steps could be performed by other entities (e.g., the application program) without departing from the spirit and the scope of the claimed invention.

FIG. 3 is a flow diagram of the steps for determining floppy disk insertions and removals in the preferred embodiment of the present invention. The purpose of this flowchart is to determine the write protect signal logic (i.e., whether the write protect signal defaults to a write protect state or a non-write protect state). Upon determining the write protect signal logic, the flow diagram periodically evaluates the changeline and write protect signals to determine insertions and removals of disks to/from the floppy disk drive. The Determine Floppy Disk Arrivals and Removals Routine begins by calling a Determine Write Protect Signal Logic Routine (step 310).

FIG. 4 is a flow diagram of the steps for determining the write protect signal's logic in the preferred embodiment of the present invention. The purpose of this flow diagram is to determine whether the write protect signal defaults to a write protect status or a non-write protect status. The routine begins processing by inputting a current value of the write protect signal (step 410). The routine continues by issuing a ReadID call to access the disk drive (step 420). This ReadID call references a ReadID function in the floppy disk controller. In brief, this function returns positioning information to the driver. The precise data returned from the ReadID function is not material to the present invention as the present invention does not utilize the ReadID function in its designed manner. Instead, and as explained in more detail in the parent application, the routine uses the ReadID function to quickly determine whether the floppy disk drive contains a floppy disk. In order to quickly determine the disk's presence or absence, the routine, prior to issuing the ReadID call, loads a time-out counter with a predetermined value. This time-out counter is used to terminate the ReadID request when the controller does not complete the request within the predetermined amount of time. More specifically, the time-out counter is decremented with each cycle of the system clock 290. When the counter is decremented to zero, "times-out," before the controller completes the processing of the ReadID function, the Determine Write Protect Signal Logic Routine automatically recaptures processing control. On the other hand, when the ReadID request does not time-out, the routine regains processing control via an interrupt. The controller 240 generates this interrupt to inform the central processing unit that the controller has completed the disk access request. In turn, the central processing unit relays the interrupt to the routine. This interrupt informs the routine that the controller was able to process the ReadID request, and thus signifies that a disk is present in the drive. When the controller does not return an interrupt within the time specified by the time-out counter, the routine stores the inputted write protect value as the default state of the write protect signal (step 430, YES Pathway, and step 440). Conversely, when the routine receives an interrupt in response to the ReadID call, the routine attempts to write data to the disk (step 430, NO Pathway, and step 445).

When the attempt to write data onto the disk is successful, the routine inverts the inputted write protect signal value and stores the inverted write protect signal value as the write protected state of the write protect signal (step 450, YES Pathway, and steps 465 and 470). When the attempt to write data onto the disk is not successful, the routine stores the inputted write protect signal value as the write protected state of the write protect signal (step 450, NO Pathway, and step 460).

At this point, the routine determines whether it knows the default state and the write protected state of the write protect signal (step 475). When both of these states are not known, the routine waits for a predetermined amount of time before re-inputting the write protect signal and repeating the above-described steps (step 475, NO Pathway, and step 480). Once the default state and the write protected state of the write protect signal is known, the routine returns processing control to the Determine Floppy Disk Arrivals and Removals Routine of FIG. 3.

The Determine Floppy Disk Arrivals and Removals Routine continues processing by periodically calling the Evaluate Changeline and Write Protect Signals Routine to determine when floppy disks are removed or inserted into the floppy disk drive (steps 320 and 330). In the preferred embodiment of the present invention, the wait period described by step 330 is typically two seconds as this is generally considered to be the minimum amount .of time necessary to exchange floppy disks from the floppy disk drive.

FIG. 5 is a flow diagram of the steps for evaluating changeline and write protect signals in the preferred embodiment of the present invention. The purpose of this routine is to determine whether an activated changeline represents a removal or an exchange of a floppy disk from the floppy disk drive. The routine begins processing by inputting the changeline and write protect signals (step 510). When the changeline is inactive, the routine determines that the disk had not been changed (step 520, NO Pathway, and step 530). When the changeline is active, the routine evaluates the write protect signal (step 520, YES Pathway, and step 540). When the write protect signal is in the default state, the present invention determines that the disk has been removed (step 540, YES Pathway, and step 550). When the write protect signal is not in the default state, the routine determines that the activated changeline represents a disk insertion (e.g., a removal and an insertion of a disk) (step 540, NO Pathway, and step 560). In the preferred embodiment of the present invention, when the routine determines that a disk has been removed (step 550) or that a disk has been inserted (step 560), the present invention communicates this event to the operating system 275. The operating system then informs the application program 280 of the event. As the Evaluate Changeline and Write Protect Signals Routine is called approximately every two seconds, the preferred embodiment utilizes a semaphore to ensure that the disk insertion message and the disk removed message are not sent repetitively (e.g., that two disk insertion messages or two disk removal messages are not sent consecutively). In the above-described manner, the present invention quickly and easily determines insertions and removals of floppy disks from a floppy disk drive. As the technique employed by the present invention does not require powering the floppy disk drive motor, the present invention consumes less power than conventional systems. By consuming less power, the present invention facilitates the development of power management timing strategies and should prolong the lifetimes of the floppy disk drive's components. As such, the present invention represents a substantial improvement over conventional systems.

The detailed discussion provided above represents only a preferred embodiment of the present invention. The above description will enable those skilled in the art to make various modifications to the preferred embodiment that do not depart from the spirit and the scope of the claimed invention. For example, those skilled in the art will appreciate that one could monitor for transitions of the write protect signal to determine when floppy disks of the non-default type are inserted or removed from the floppy disk drive. By monitoring for such transitions, it would not be necessary to evaluate the status of the changeline. Accordingly, the present invention encompasses all such modifications that read on the appended claims and equivalents thereof.