PLC Circular Counter ladder diagram instruction in LDMicro

A circular counter increase or decrease its content whenever the input change its logic state. When its content reaches its maximum value, it will roll over to the initial value on the next count. The input logic state could be - from high to low or from low to high.

Circular Counter Up (CTC) and Circular Counter Down (CTR)

There are two instructions for circular counter, a circular counter up (CTC) and a circular counter down (CTR). Here we discuss about a CTC.

CTC instruction property

When the Max value is reached, the increment will start from 0 on the next count.

The example below use this instruction to count an input for every one second.

An introductory example of using CTC

A cyclic on/off timer create a one second pulse that fed the CTC. Click here to download the ladder diagram example.