Counters in PLC Types of PLC Counter
Counters in PLC | Types of PLC Counter Counters count rung transitions. The CTU runs the accumulated value of the counter up on the false to true rung transition, and the CTD instruction runs the accumulated value down. The CTU and CTD can be used in conjunction with each other. Counters consist of the following components: ACC Accumulated Value PRE Preset Value CD Count Down Bit CU Count Up bit OV Overflow Bit UN Underflow bit By default, data file C5 stores counters, however, other counter files can be added as well. Below is how the C5 Data file would appear: For the CTU instruction: The CU bit is high when the CTU instruction is true. The ACC value increments by the value of 1 each time the CU bit goes high. When the ACC reaches the PRE, the DN bit will be set. The CTU will continue to increment the accumulated value until it reaches the maximum possible value for a 16 bit signed integer (32767). If the ...