A PLC executes an initialization step when placed in run mode, then repeatedly executes a scan cycle sequence.
PLC scan cycle
The basic PLC scan cycle consists of three steps
- An input scan
- A user program scan
- An output scan
The total time for one complete program scan is a function of processor speed, I/O modules used, and length of user program
Typically, hundreds of complete scans can take place in 1 second or less.
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