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DOS Interface to Non-Dos Formatted Diskette Drives

IP.com Disclosure Number: IPCOM000059621D
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 36K

Publishing Venue

IBM

Related People

Pekowski, RP: AUTHOR

Abstract

A method is described that provides a DOS compatible interface to non- DOS formatted diskette drives. More specifically, it provides an interface to Displaywriter diskette drives, thus allowing the transfer of documents between Displaywriters (DW) and Personal Computers (PC). This arrangement makes it possible for a PC running DOS to interface to any non-DOS formatted disk/diskette drive by the simple implementation of a device driver for that device.

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DOS Interface to Non-Dos Formatted Diskette Drives

A method is described that provides a DOS compatible interface to non- DOS formatted diskette drives. More specifically, it provides an interface to Displaywriter diskette drives, thus allowing the transfer of documents between Displaywriters (DW) and Personal Computers (PC). This arrangement makes it possible for a PC running DOS to interface to any non-DOS formatted disk/diskette drive by the simple implementation of a device driver for that device. Note that the disk/ diskette drive need not be directly attached to the Personal Computer's hardware, but can be connected via a communication link. This flexibility is inherent in the described interface. Some possible non-DOS formatted disk/diskette drives that this arrangement makes it possible to interface to are the Displaywriter diskette drives, 5520 diskette drives, 5218 diskette drives, and IBM Series/I diskette drives. The DW is used as an example in the following description. Note that any other non-DOS formatted disk/diskette drive could be substituted for the DW: The only limitations to this arrangement are as follows: - DOS 2.0 or above must be used. - DW documents must be accessed sequentially. - No more than a predefined number of documents can be opened at one time. - No paths or sub-directories can be created on the DW diskettes.

There are two unique characteristics to this arrangement: 1. A new device driver interface to DOS 2.0 called Open/Close/Read/ Write (OCRW) device driver is defined. DOS provides a device driver interface for adding new diskettes drives (block devices) to the PC. This interface is via read sector and write sector commands. DOS attempts to read and write sectors on a DW diskette as if the diskette was formatted just like any other DOS diskette. This is a problem because the Displaywriter does not format diskettes the same way as DOS. 2.

A communications protocol for transferring documents between DWs and PCs is defined. There currently exists protocols for transferring documents between Displaywriters and PCs, but this one is unique in two ways. First, it allows documents to be selectively transferred, while other protocols require all documents on a diskette to be transferred. Second, it allows documents to be transferred in either direction, while other protocols only allow transfer from Displaywriter to PC. Fig. 1 illustrates the normal DOS device driver environment on the PC. The user types in a command on the keyboard (i.e., COPY or ERASE) using drive letters (i.e., A or B) to specify which diskette device is being accessed. The application program gets executed and converts these drive letters into drive numbers and issues DOS function calls (interrupt X'21') to access the requested diskette device. DOS determines from the drive number which device driver to call, which sectors to read or write on that device, and calls the device driver to perform the function. Fig. 2 illustrates the mo...