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Process Interrupt Algorithm

IP.com Disclosure Number: IPCOM000077910D
Original Publication Date: 1972-Oct-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Nagel, DM: AUTHOR

Abstract

Process Interrupt (or PI) is a hardware method of asynchronously interrupting a processor, as a result of a logical change in one or more of the external digital signals into the hardware comparison of a loadable reference register and the input signals. When a transition occurs, the interrupt directs the software to a routine that must read the input signals and make decisions based on the current inputs, the reference value, and the significance of the determined changes.

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Process Interrupt Algorithm

Process Interrupt (or PI) is a hardware method of asynchronously interrupting a processor, as a result of a logical change in one or more of the external digital signals into the hardware comparison of a loadable reference register and the input signals. When a transition occurs, the interrupt directs the software to a routine that must read the input signals and make decisions based on the current inputs, the reference value, and the significance of the determined changes.

Significance of the input transitions can be specified in one of four possible categories: Category Description

1 Neither a zero-to-one or a one-to zero transition

of the input signal is significant

2 Only the zero-to-one transition is significant

3 Only the one-to-zero transition is significant

4 Both possible transitions of an input signal

are significant. This algorithm allows category specification by bit position for each input signal, so that determination of whether or not the interrupt resulted from an input transition that is of significance may be made rapidly in a common routine. Category specification is done in two words of main storage labeled "ON" and "OFF" which correspond bit-for-bit with the input signals. The following shows how to configure these two words, to specify to the algorithm which category of significance applies to each input bit. Input Bit X OFF Word ON Word

Category Bit X Bit X

1 0 0

2 0 1

3 1 0

4 1 1

The following logic equation is the basis of the algorithm: OUT = (ON).(INPUT) (REF) + (OFF) (INPUT)(REF) where:
OUT is a bit in position X of a reg...