Define with respect to PLC i) scanning cycle ii) speed of execution.

Define with respect to PLC i) scanning cycle ii) speed of execution.
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1 Answer

Answer :

Scanning Cycle * It is number of states/steps which the controller follows when it is put in RUN mode. * It is also called as operating cycle and is defined as “the number of states through which the controller scan the program before execution” * The loaded program is kept in memory of PLC and every time the program will be scan by the PLC. It has four states which are shown in fig. below. 

image

The significance of scan cycle in PLC is to test the program and make it error free by going through above four states i.e. self test, input scan, program scan and output scan. 

Speed of execution: The speed at which PLC scans memory and executes the program is referred as a speed of execution. Higher CPU speeds provide faster performance that shortens task time. 

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