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Format Command Processing in a Diskette Adapter

IP.com Disclosure Number: IPCOM000039772D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Davis, KD: AUTHOR [+2]

Abstract

This article describes a format command implementation used in a diskette adapter. A single command interface provides minimal host processor and bus activity, while the format process provides rigorous media verification and optimal performance. The process formats and verifies the media in two quick passes. The first pass formats and verifies a stress pattern in two revolutions per track. The second pass verifies proper cylinder placement, scanning the diskette in greater than six cylinders per diskette revolution. Error recovery is completely internal to the diskette adaptor. The format command also creates and maintains an error map and statistical information record. The algorithm in the figure illustrates the format process.

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Format Command Processing in a Diskette Adapter

This article describes a format command implementation used in a diskette adapter. A single command interface provides minimal host processor and bus activity, while the format process provides rigorous media verification and optimal performance. The process formats and verifies the media in two quick passes. The first pass formats and verifies a stress pattern in two revolutions per track. The second pass verifies proper cylinder placement, scanning the diskette in greater than six cylinders per diskette revolution. Error recovery is completely internal to the diskette adaptor. The format command also creates and maintains an error map and statistical information record. The algorithm in the figure illustrates the format process. Initially, the format process seeks to cylinder 0 (1) to read the statistical information record (SIR). The SIR contains information describing the number of times the diskette has been formatted, the number of head wear revolutions, the number of resettable temporary errors, the number of resettable permanent errors, the number of temporary errors since the creation of the SIR and the number of permanent errors since the creation of the SIR. If an SIR does not already exist, the format process creates an initial SIR. The format process maintains the SIR in memory for update when the process completes
(2). The format process also initializes a buffer with stress pattern data (3)A. The stress pattern data is a repeated pattern of three nibbles with a value of 'DB6' in hexadecimal. The format process formats and verifies each physical cylinder from 0 through 76 (4). Each cylinder is formatted and verified in steps (5) through (13). While accessing a track, the process sets up counters and hardware registers specifying the recording characteristics of the current track. After detecting an index, the format process instructs the interface to write a post- index gap. Following the post-index gap, the format process writes the characteristic number of sectors on the track. Each sector data record consists of the stress pattern from the initialized buffer. After writing the track sectors, the format process writes a pre-index gap until it detects the index once more. To verify that the data written to the track can be read correctly, the format process checks each sector (8). To check a sector, the interface reads the track...