Constant Scan - Mitsubishi Electric L02SCPU User's Manual And Reference

3.2

Constant Scan

Scan time of the CPU module is not constant because the processing time varies depending on the execution status of
instructions used in a program. By using this function, scan time can be maintained constant.
(1) Application
I/O refresh is performed before program execution. By using this function, the constant I/O refresh intervals can
be maintained even the time required for program execution changes.
• Scan time without constant scan setting
• Scan time with constant scan setting (7ms)
• Scan time for multiple programs with constant scan setting (10ms)
(2) Constant scan time setting
The setting range is from 0.5 to 2000ms (in increments of 0.5ms).
When not using the constant scan function, leave the setting box blank.
Project window  [Parameter]  [PLC Parameter]  [PLC RAS]
The constant scan accuracy is 0.01ms. However, constant scan time may increase when an interrupt program or
a fixed scan execution type program is being executed.
Program execution
END processing
END 0 END 0
5ms
Program execution
END processing
END 0 END 0
Waiting time
5ms
2ms
7ms
Waiting time
8ms
10ms
Enter a value.
CHAPTER 3 CPU MODULE FUNCTIONS
END 0 END 0
6ms 5ms
END 0 END
5ms
6ms 1ms 2ms
7ms 7ms
Execution of program A
Execution of program B
Execution of program C
END processing
2ms 9ms 1ms
10ms
0
3
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