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Browse Prior Art Database

Error Detection in Decoding Controllers

IP.com Disclosure Number: IPCOM000088195D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Curlander, PJ: AUTHOR

Abstract

A controlled unit receives instructions and selection signals over a BUS OUT from a controlling unit (not shown). It is the responsibility of the controlled unit to respond to a selection sequence, poll sequence or a status select sequence. The latter sequence is achieved in a controlled unit having a programmable processor (not shown) in the other portion of the controlled unit by hard logic circuits which are separate and independently operable from the controlled unit processor. Such status reporting allows status to be supplied to a controlling unit without interrupting the programmed processor or requiring that the programmed processor be operating successfully.

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Error Detection in Decoding Controllers

A controlled unit receives instructions and selection signals over a BUS OUT from a controlling unit (not shown). It is the responsibility of the controlled unit to respond to a selection sequence, poll sequence or a status select sequence. The latter sequence is achieved in a controlled unit having a programmable processor (not shown) in the other portion of the controlled unit by hard logic circuits which are separate and independently operable from the controlled unit processor. Such status reporting allows status to be supplied to a controlling unit without interrupting the programmed processor or requiring that the programmed processor be operating successfully.

The above listed three functions are mutually exclusive. As such, the three decode functions are separated into three units; the unit select and operation decode, poll and poll function decode, and status select and status selection. All three units continuously monitor BUS OUT. Whenever an operation to the specific controlled unit occurs, all three units should detect the request and all units activate their respective operation detection lines, labeled A. As a function of whether the requested BUS OUT signals concern a selection, poll, or status select, the appropriate responder will be activated by one of the decoding units. The responders, when activated, supply an indicating signal over their respective lines B indicating a response is being generated to be supplied over BUS IN to the controlling unit(s).

To ensure faithful operation, the illustrated checking logic detects errors whenever an incoming request is decoded and no responder supplies signals over BUS IN, if a responder supplies signals over BUS IN when there is no request on BUS OUT as detected by the decode units, if no decode unit detects which operation is to be performed or if more than one responder is activated. For illegal responses the controlling unit will detect those failures. Further, connections b...