Browse Prior Art Database

Degatable Field Replaceable Unit

IP.com Disclosure Number: IPCOM000086317D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Hitt, DC: AUTHOR [+2]

Abstract

A degatable field replaceable unit is a method for designing digital electronic systems, which are capable of being diagnosed to a single field replaceable unit (FRU).

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Degatable Field Replaceable Unit

A degatable field replaceable unit is a method for designing digital electronic systems, which are capable of being diagnosed to a single field replaceable unit (FRU).

All logic FRU's 10 have a single input which will degate all external drivers and terminate in the special terminator 12. Terminator 12 has a terminating resistor 14, a receiver 16, and a driver 18. The receivers and drivers are selectable through a fan-in/fan-out network to the maintenance subsystem providing external testing and control of each external net.

Normal transmission line terminating conventions are followed when the net is driven from the logic unit driver end of the net. However, when the net is driven from the terminator end of the net, transmission line reflections will exist. These reflections can be observed through the receiver by the maintenance subsystem and the net reflections can be measured.

In this environment single FRU isolation can be obtained by implementing the following sequence. 1. All logic FRU's 10 are degated and all external nets are tested for the undriven state. 2. All logic nets are driven from the terminator 12 end of the net and tested for the driven state as seen through receiver 16. 3. All nets (one at a time) are clocked and the reflections (echo) measured. This measurement is compared to a correct result file maintained in the maintenance subsystem. 4. All logic FRU's are tested (one at a time) by removing the degate sig...