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Browse Prior Art Database

Large Scale Integration Diagnostic Device

IP.com Disclosure Number: IPCOM000052941D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 3 page(s) / 78K

Publishing Venue

IBM

Related People

Benfer, FM: AUTHOR [+3]

Abstract

Incorporating diagnostic hardware into large-scale integrated (LSI) circuit chips can aid in the diagnosis of hardware failures.

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Large Scale Integration Diagnostic Device

Incorporating diagnostic hardware into large-scale integrated (LSI) circuit chips can aid in the diagnosis of hardware failures.

In LSI technology, the smallest field replaceable unit (FRU) is likely to be a complex and expensive item. This being the case, it is advantageous to have diagnostic programs that can isolate machine failures to a single FRU or a very small group of FRUs. The device shown is especially useful for FRU isolation in an environment having many LSI chips mounted on a single substrate. The FRU in this environment is a fully populated substrate, which is a costly item. The design of the device presumes two other design features to be true: (1) there is a log-out mechanism for making the state of machine triggers available to diagnostic programs; and (2) ``long'' signal-carrying wires require termination. If these ``long'' wires do require termination, then it is usually the case that FRU-to- FRU signals will be terminated, since FRU-to-FRU distance is adequately ``long.''

The device takes advantage of this common factor of most FRU-to-FRU signals. It puts diagnostic circuitry on the terminator chip (terminating resistors are likely to be packaged together on LSI terminator chips), and enables diagnostic programs to verify that almost every FRU input signal is at a known state. This is an improvement over typical existing techniques, which only verify that triggers are at known states. Since there is logic circuitry between those triggers, some of which may be on different FRUs, the existing techniques have difficulty resolving which FRU has the failing circuitry.

The...