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Programmable Loop Back Read Diagnostic for Disk Drive

IP.com Disclosure Number: IPCOM000076053D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Miller, TH: AUTHOR [+3]

Abstract

The disk drive attachment read/write logic 5 can be checked under CPU program control to isolate disk drive failures from attachment failures.

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Programmable Loop Back Read Diagnostic for Disk Drive

The disk drive attachment read/write logic 5 can be checked under CPU program control to isolate disk drive failures from attachment failures.

In the normal write mode with write signal 16, constants and data from CPU 7 are serialized by serializer 8 and sent over line 40 to disk drive 9, under control of write oscillator 10 and attachment clock 11. This data is also used by the normal read circuitry including data separator 25, deserializer 12, and read register 26, and is deserialized by deserializer 12 and is used by check-byte generator 13 to generate check bytes which are written on disk drive 9. There are three check bytes, and these are respectively generated as follows: (1) the first check byte is an Exclusive OR result of the odd bytes of the data transmitted to disk drive 9; (2) the second check byte is the Exclusive OR result of the even bytes of data transmitted to disk drive 9; and (3) the third check byte is the LRC (longitudinal redundancy check) byte of all of the bits transmitted to drive 9.

In the normal read mode with signal 17, the data from disk drive 9 controls variable-frequency oscillator 14 which runs the attachment clock 11. The data from disk drive 9 passes through data separator 25 and is deserialized by deserializer 12. The check bytes are generated by check-byte generator 13 due to this data and the data from disk drive 9 is sent to CPU 7 through separator 25, deserializer 12, read register 26, and 8-byte data storage buffer 15. In reading, the same check bytes, as above described, are generated by check-byte generator 13, but from the data received from disk drive 9; and the three check bytes thus generated from the data from drive 9 are compared with the three bytes ge...