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CHAPTER 3 CPU MODULE FUNCTIONS
3
3.2 Constant Scan
(a) Condition
Set a value that satisfies the following relational expression.
WDT setting time > Constant scan setting time > Maximum scan time of the program
If the program scan time is longer than the constant scan setting time, the CPU module detects "PRG. TIME
OVER" (error code: 5010). In this case, the constant scan setting is ignored and the program scan time is
applied.
If the program scan time is longer than the WDT setting time, the CPU module detects "WDT ERROR". In this
case, the program execution is stopped.
(3) Waiting time from when END processing is executed until next scan starts
• When an interrupt factor occurs during waiting time, either of an interrupt program or fixed scan execution
type program is executed.
• When a service processing parameter is set, a communication service processing with peripherals and
intelligent function modules is performed.
0 0 END 0END 0END 0END
3.5ms
4ms 4ms
3.8ms 3.4ms
4ms5.3ms
0.2ms
0.5ms
0.6ms
When constant scan time is set to 4ms
Program execution
Scan where scan time is increased
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