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Apparatus for Counting to a Predetermined Number

IP.com Disclosure Number: IPCOM000080091D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Dingee, HA: AUTHOR [+3]

Abstract

The apparatus of the drawing produces a signal on a line 2 when a predetermined number of events has been counted. This number, N, is provided in a register 3. An arithmetic device 4 subtracts 1 from the number and loads a counter 5 with the number N-1. As each event occurs, a decrement pulse appears on a line 7 and decrements counter 5. Thus, the apparatus counts down from N-1 to -1 instead of conventionally counting down from N to 0.

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Apparatus for Counting to a Predetermined Number

The apparatus of the drawing produces a signal on a line 2 when a predetermined number of events has been counted. This number, N, is provided in a register 3. An arithmetic device 4 subtracts 1 from the number and loads a counter 5 with the number N-1. As each event occurs, a decrement pulse appears on a line 7 and decrements counter 5. Thus, the apparatus counts down from N-1 to -1 instead of conventionally counting down from N to 0.

Counter 5 has an additional leftmost bit position 6 that is not needed for storing the number N-1 and is set to 0 for the counting operation. Thus, when counter 5 holds a 0 in each bit position, the operation has reached the next to the last number that is to be counted. With the next decrement pulse on line 7, the rightmost bit position of counter 5 is changed from a 0 to a 1, and 1's propagate from stage-to-stage through the counter to produce a 1 in the leftmost position 6. The associated 1 logic level signal on line 2 signals the end of the count. This apparatus avoids the decoding logic that would otherwise be provided for detecting the occurrence of a 0 in each stage of register 5.

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