Browse Prior Art Database

Concurrent Seek and Read/ Write For Floppy Diskette Controller

IP.com Disclosure Number: IPCOM000048495D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Krishnamurty, R: AUTHOR [+2]

Abstract

Many floppy diskette controllers (FDCs) inherently preclude any overlap of read or write commands with seek or restore commands. The disclosed diskette adapter partially solves this problem by the inclusion of a dedicated microprocessor (DCP) in the adapter design, as shown in Fig. 1. Normally, a seek command is passed to the FDC from the system processor. The FDC determines the number of step pulses to be issued, the direction of the step (up or down), and the time between step pulses. The DCP, however, intercepts the step and direction lines and uses them to alter the contents of a cylinder number register (CYL REG) contained within the RAM (random-access memory) of the DCP. The contents of the CYL REG are encoded and transmitted to the diskette drive on the access lines.

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Concurrent Seek and Read/ Write For Floppy Diskette Controller

Many floppy diskette controllers (FDCs) inherently preclude any overlap of read or write commands with seek or restore commands. The disclosed diskette adapter partially solves this problem by the inclusion of a dedicated microprocessor (DCP) in the adapter design, as shown in Fig. 1. Normally, a seek command is passed to the FDC from the system processor. The FDC determines the number of step pulses to be issued, the direction of the step (up or down), and the time between step pulses. The DCP, however, intercepts the step and direction lines and uses them to alter the contents of a cylinder number register (CYL REG) contained within the RAM (random-access memory) of the DCP. The contents of the CYL REG are encoded and transmitted to the diskette drive on the access lines. These access lines directly drive the stepper motor on the drive.

A modified REG/PORT command is defined that can be used to independently alter the state of the access lines and the CYL REG. This command can be applied to produce a single-track step function that the DCP executes independently of the operation in progress within the FDC. The following logic must be resident within the system software in order to use the single track step command: If the single-track step command structure is used in place of seek commands to the FDC, then a read or write command can be independently issued to the FDC, effectively producing overlap...