Operating Cycle of the PLC Processor Flashcards
What is the processor scan?
Reading the inputs, solving the program and writing to the outputs
What is required to capture high-speed switching events using a pLC with a longer scan time?
Special programming instructions with interrupts or high-speed counter inputs
If the PLC has a scan time of 9ms and is required to monitor a signal that ___________, the CPU will never notice the signal has changed state.
a. changes state once in 12ms
b. changes state very slowly
c. changes state once in 20ms
d. changes state twice in 5ms
d. changes state twice in 5ms
Scan time is the time required ____________
To execute one cycle of the processor scan
If the state of the inputs changes during the program scan, when does that change take effect?
During the start of the next program scan
What are three items on which the scan time of the processor depends?
- Speed of the CPU
- Length of the program
- Total number of I/O to service
- Type of programming instructions
During what portion of the operating cycle of a PLC does the processor read the input status and write to the outputs?
I/O Update