Browse Prior Art Database

Auto Retry Apparatus for Diskette Controllers

IP.com Disclosure Number: IPCOM000051305D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Ott, WB: AUTHOR [+2]

Abstract

Conventional floppy diskette controllers search for data until two inde pulses have been received, thereby indicating at least one complete revolution of the diskette. Such a scheme does not allow for an automatic retry in the event data is not found during the initial time between the two index pulses.

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Auto Retry Apparatus for Diskette Controllers

Conventional floppy diskette controllers search for data until two inde pulses have been received, thereby indicating at least one complete revolution of the diskette. Such a scheme does not allow for an automatic retry in the event data is not found during the initial time between the two index pulses.

The circuit shown in the figure allows an automatic retry in the event that data is not found in the initial pass. After a read/write command is issued to the floppy diskette controller (FDC) 1, it searches for the target data until it is either found or until two index pulses are encountered. If two index pulses occur first, the operation is ended and a data-not-found signal is posted. If the target date is first found, the operation completes normally. The target of data is only presented to the FDC once between two index pulses.

To provide an auto-retry feature, it is necessary that, when the read/write command is issued to the FDC, the FDC informs the main controller 2 that a read/ write command has started. This starts a timing cycle in the main controller, which maintains an output signal until the FDC indicates the end of the operation or until the main controller times out. Once the main controller times out, the output signal enables the gate 3 to permit index pulses to be applied to the FDC, and after two such index pulses have occurred, the end of operation signal resets the controller.

By using this circuit...