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Self Checking CRC Generator

IP.com Disclosure Number: IPCOM000079140D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Golla, JR: AUTHOR [+2]

Abstract

A self-checking cyclic-redundancy check (CRC) generator detects malfunctions in the generator, by first operating the generator in a true mode data is readback. If no malfunction exists, the CRC in the complement form will be exactly opposite. Any variation is an error.

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Self Checking CRC Generator

A self-checking cyclic-redundancy check (CRC) generator detects malfunctions in the generator, by first operating the generator in a true mode data is readback. If no malfunction exists, the CRC in the complement form will be exactly opposite. Any variation is an error.

In the figure, the CRC generator includes register 10 having sixteen positions and logic for a CRC generator polynomial x16+x12+x5+1. The success of detecting a CRC generator error, of course, does not depend upon the particular CRC generator polynomial. The CRC is generated by first resetting all of the positions of register 10 to zero. The accumulate Check control line 16 is made active and the data to be written, In Data, on conductor 17, is applied to exclusive 0R circuits 15 and 50. The data is passed by 15 to AND circuit 20 and by 50 to a device such as a disk file, not shown. Exclusive OR 50 passes the data without any inversion, because at this time the output of AND circuit 45 is zero. On the other hand, a Write control signal is applied to exclusive OR circuit 40 and the output of 40 feeds exclusive OR circuit 15. This causes an inversion of the output of 15. AND circuit 20 passes the inverted data to exclusive OR circuit 25, which also has an input for receiving the Write control signal. The output of 25 feeds the first position of register 10. AND 20 also passes the inverted data to exclusive OR circuits 30 and 35, which are connected to positions five and t...