Browse Prior Art Database

Interrupt Error Checking

IP.com Disclosure Number: IPCOM000078200D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Bonczek, R: AUTHOR

Abstract

A scheme is shown to check for correct trap operations in a processor. Presently, taking the wrong trap or trapping to an indeterminate word results in an undetected error. A method is described, whereby all traps are taken to a particular word type used only for traps. This trap word will branch or compare on the trap which is being requested. If the branch or compare is incorrect, it is an error. If during a trap cycle the word being executed is not a trap word type, it is an error.

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Interrupt Error Checking

A scheme is shown to check for correct trap operations in a processor. Presently, taking the wrong trap or trapping to an indeterminate word results in an undetected error. A method is described, whereby all traps are taken to a particular word type used only for traps. This trap word will branch or compare on the trap which is being requested. If the branch or compare is incorrect, it is an error. If during a trap cycle the word being executed is not a trap word type, it is an error.

Fig. 1 illustrates a higher priority request made during the execution of a sequence of instructions. The current execution is interrupted and an exit is forced to begin the execution of the P1 priority subroutine

At this time, two errors can occur, i.e. the wrong priority subroutine is entered (Error 1), or the exit is to an unknown instruction (Error 2).

The first instruction of each priority subroutine branches on the priority request signal. If the priority request for this priority subroutine is not present, Error 1 is indicated.

The first instruction of every priority subroutine contains a bit or bits which do not appear in any other instruction in the system. A hardware compare of this bit or bits is made with the priority request signal (Fig. 2). If there is a miscompare, the Error 2 indication is generated.

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