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Stored Cyclic Redundancy Check Buffered Data Integrity Checking

IP.com Disclosure Number: IPCOM000085224D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Mosser, HV: AUTHOR [+2]

Abstract

Hardware for attaching input/output (I/O) devices to controllers often includes data buffering and cyclic redundancy check (CRC). The integrity of the buffered data can be checked using reduced buffer hardware and with enhanced error detectability relative to parity checking, by use of stored CRC characters.

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Stored Cyclic Redundancy Check Buffered Data Integrity Checking

Hardware for attaching input/output (I/O) devices to controllers often includes data buffering and cyclic redundancy check (CRC). The integrity of the buffered data can be checked using reduced buffer hardware and with enhanced error detectability relative to parity checking, by use of stored CRC characters.

A CRC word is generated on the data record as it is put into the buffer. The generated CRC word is stored following the last data word (N) of the record as represented in the block designated buffer in the figure.

When the data record is read out of the buffer, a CRC word again is generated, and after data word N is read out the CRC word, just generated, is compared to the next following word read out of the buffer, which is the CRC word first generated when the data record was put into the buffer. If the two CRC words match, the data record just read from the buffer is deemed error-free.

Suitable logic hardware for carrying out the stored CRC checking method is represented by the figure. Timing definitions for the gate lines shown in the figure are as follows: G 1 = Source to buffer and not CRC time.

G 2 = Device to buffer.

G 3 = Buffer to source and not CRC time.

G 4 = Buffer to device and not CRC time.

G 5 = Buffer to device and CRC time.

G 6 = G12 delayed (time for compare to resolve).

G 7 = G11 delayed.

G 8 = Device to buffer or source to buffer and CRC time.

G 9 = G3 or G4.

G10 = G1 or G2 (...