CHAPTER6 FUNCTIONS
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6.2 Constant Scan
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(3) Constant scan time setting
Set a constant scan time value in the PLC RAS tab of the PLC parameter dialog box.
The setting range is 0.5 to 2000ms (in increments of 0.5ms).
When not executing the constant scan function, leave the constant scan time setti ng box blank.
(a) Condition
The constant scan time needs to satisfy the following relational express ion.
If the sequence program scan time is longer than the constant scan setting ti me, the CPU module
detects “PRG. TIME OVER” (error code: 5010).
In this case, the constant scan setting will be ignored and the sequenc e program scan time will be
applied.
If the sequence program scan time is longer than the WDT setting time, the CPU module detects
“WDT ERROR”.
In this case, the program execution will be stopped.
Figure 6.2 When the constant scan time is set to 10ms
(WDT setting time) > (Constant scan setting time) >
(Sequence program maximum scan time)
Figure 6.3 Operation when the scan time is longer than the constant scan setting time
Set a constant scan
time value here.
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3.5ms 0.5ms
4ms 4ms
3.5ms 3.4ms 0.6ms
4ms5.3ms
5ms
0.5ms
Scan where the constant scan setting is not applied
Constant scan setting (4ms)
Constant
scan
Sequence
program