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Sector Pulse Check Circuit

IP.com Disclosure Number: IPCOM000088119D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 4 page(s) / 107K

Publishing Venue

IBM

Related People

Dawson, H: AUTHOR [+3]

Abstract

In a disk storage drive, sector pulses are read from the file media and sent to the attachment which connects the disk storage drive within a computer system. The file media contains a plurality of concentric tracks and each track is divided into sectors. The start of a track or the first sector is identified by an index timing pulse. Thereafter, the location of each next sector is identified by a sector pulse. The attachment, upon receipt of a sector pulse, causes data to be read from or written onto the file media in the associated sector. Any sector pulse caused by noise or the absence of a sector pulse can cause the attachment to initiate or continue a read or write operation erroneously. The sector pulse check circuit detects false and missing sector pulses.

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Sector Pulse Check Circuit

In a disk storage drive, sector pulses are read from the file media and sent to the attachment which connects the disk storage drive within a computer system. The file media contains a plurality of concentric tracks and each track is divided into sectors. The start of a track or the first sector is identified by an index timing pulse. Thereafter, the location of each next sector is identified by a sector pulse. The attachment, upon receipt of a sector pulse, causes data to be read from or written onto the file media in the associated sector. Any sector pulse caused by noise or the absence of a sector pulse can cause the attachment to initiate or continue a read or write operation erroneously. The sector pulse check circuit detects false and missing sector pulses.

Each data track 10 (Fig. 1) has sixty sectors which are separated by sector pulses. The sector pulses for indicating the beginning of sectors are generated from a servo track 15. Each sector of data track 10 contains 300 bytes of data. A sector pulse is two-byte times long. In addition to causing the sector pulses to be generated, the servo track also causes write clock signals to be generated. There are 2400 write clock pulses between sector pulses, each write clock pulse having a period of 140 ns.

The clock pulses are applied to a counter 25 (Fig. 2) to generate +CNTR4 pulses which have a two-byte duration. Thus, there are 150 +CNTR4 pulses between sector pulses. The +CNTR4 pulses are applied to eight-stage counter 25, whose outputs are decoded by AND circuits 26 and 27 to indicate a count of 148 and 150 +CNTR4 pulses, respectively.

AND circuit 26 controls the setting of window latch 28, while AND circuit 27 controls the reset thereof via OR circuit 29. Window latch 28 provides a signal for examining when a sector or index pulse occurs. Counter 25 advances on the rising edge of a +CNTR4 pulse. Latch 28...