Browse Prior Art Database

Enhanced Error Detection for Storage Media

IP.com Disclosure Number: IPCOM000086323D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Datres, JH: AUTHOR [+2]

Abstract

This parity scheme has the ability to detect complete failure of the storage media without the use of complex error correcting codes.

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Enhanced Error Detection for Storage Media

This parity scheme has the ability to detect complete failure of the storage media without the use of complex error correcting codes.

Error detection in data processing equipment has generally been accomplished by the addition of an extra data bit to a byte (8 bits), called the parity bit, where the function of this bit is to make the total number of bits that are on (a 1) odd (for odd parity) or even (for even parity). In the event that the entire byte fails and the failure results in all 1's, odd parity cannot detect the failure. If the failure results in all 0's, even parity cannot detect it.

This short coming of a simple parity error detection system can be eliminated by making the sense of the parity (odd vs even) a function of the storage address. The figure shows the application of the concept to a 2-byte wide physical entity. For more than 2 bytes the logic is simply replicated. For a single byte only the left side of the media applies.

When the low-order address bit is on (a 1) signifying an odd address, the parity bit for byte 0 will be inverted resulting in the storage of even parity for byte
0. Since the low-order address bit is inverted and applied to the other parity bit, the parity for byte 1 is stored as odd. Likewise, when the low-order address bit is off, byte 0 parity will be stored as odd and byte 1 will be stored as even.

In the event of a full failure of the storage media and since one byte is store...