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Variable Timing Window for Line Interrogation

IP.com Disclosure Number: IPCOM000088089D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Kort, RR: AUTHOR [+3]

Abstract

This circuit provides a means for determining whether a signal has appeared on an interrogated line before, during or after a particular time interval.

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Variable Timing Window for Line Interrogation

This circuit provides a means for determining whether a signal has appeared on an interrogated line before, during or after a particular time interval.

A first counter CNTR 1 is initialized with a number that will be decremented to zero during the period of time which precedes the time interval in which a signal should have appeared on the interrogated line 1. As long as CNTR 1 does not contain zero, the output of circuit 2 will enable AND circuit A1 to pass decrementing pulses from line 3 to CNTR 1 to continue decrementing it towards zero. (If CNTR 1 cannot be decremented below zero, then A1 will not be necessary.) While CNTR 1 is being decremented, the output of circuit 2 will enable AND circuit A2 to transmit a signal that might appear on line 1, thereby indicating on line 4 that the interrogated line carried a signal too early.

At the same time that CNTR 1 was initialized, a second counter CNTR 2 would have been initialized. The number set in CNTR 2 will be decremented to zero during the time interval in which a pulse should have appeared on interrogated line 1. While CNTR 2 does not contain zero, one leg of AND circuit A3 will receive a positive input from inverter which is fed by zero detection circuit
5. (If CNTR 2 cannot be decremented below zero, A3 and I can be eliminated.) After CNTR 1 has been decremented to zero, the output of zero detection circuit 6 will enable AND circuit A4 to pass the decrement signa...