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PLC: Incremental Count of N Pulse Input

FAQ No. FAQ01024

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How do I write a program that uses index registers and increment instructions to do an incremental count of N pulse inputs?


The following introduces a method to count 32 pulse input bits within a loop program using FOR-NEXT instructions and an index register. (FOR-NEXT instructions can be used on CS1 and CJ1 Programmable Controllers (PLC).)

Key Points About This Program

Under basic operating principles, differentiated instructions and instructions with the @ option cannot be used within loop programs. Therefore the program in the following figure has been used.

Basic Structure of a Program to Generate Differentiated Bit


Count input bits: CIO 0.00 to CIO 1.15 (32 bits): Processed with index register IR0
BCD, 4 digits, incremental counter: D100 to D131 (32 bits): Processed with index register IR1
Differentiated Bit Generated Flag: W0.00 to W1.15 (32 bits): Processed with index register IR2