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Logic Circuit Faults Located by Block Check Character Analysis

IP.com Disclosure Number: IPCOM000085281D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Simon, B: AUTHOR

Abstract

Logic circuits in digital machines are often packaged on a plurality of replaceable units such as cards which can be plugged into boards or wired sockets. Whenever a command or response is sent between two machines of a system, some form of error detection is employed, the simplest being parity bits. Often the simple error detection parity bit capability is extended to error correction, by using block check characters having a plurality of bits.

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Logic Circuit Faults Located by Block Check Character Analysis

Logic circuits in digital machines are often packaged on a plurality of replaceable units such as cards which can be plugged into boards or wired sockets. Whenever a command or response is sent between two machines of a system, some form of error detection is employed, the simplest being parity bits. Often the simple error detection parity bit capability is extended to error correction, by using block check characters having a plurality of bits.

With a reasonable amount of advance empirical analysis, test routines containing command sequences and expected responses can be developed, wherein the associated block check characters indicate not only that a correctable error occurred but also point to a probably failing replaceable unit.

The advance empirical analysis comprises exercising a digital machine with each of the commands in its repertoire, while one fault at a time is purposely created in its logic circuits by disabling a logic gate or multistate circuit, or by opening or shorting a circuit branch in a replaceable unit or at a replaceable unit input or output connector socket. A record is made of the block check character received as part of the response to each command for each of the purposely created faults.

Thereafter, a failing machine can be exercised with the repertoire of commands, while comparing the block check characters received in response to the commands with the recorded character...