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APPENDICES
APPEN
DIX
Appendix 2 CPU Module Processing Time
Appendix 2.1 Time Required for Each Processing Included in Scan Time
The CPU module measures current, minimum, and maximum values of the scan time. The scan time can be checked
by monitoring SD520, SD521, and SD524 to SD527, as the scan time is stored in the special register. (Accuracy:
±0.1ms)
When the stored values in SD520 and SD521 are 3 and 400 respectively, the scan time is 3.4ms.
(1) I/O refresh time
Use the following expression to calculate the I/O refresh time. Note that the I/O refresh time for the built-in special
functions is excluded.
[I/O refresh time]
(Number of input refresh points
*1
× KM1) + (number of output refresh points
*2
× KM2) [µs]
*1 The number of input refresh points is the value obtained by dividing the number of input points by 16/h.
*2 The number of output refresh points is the value obtained by dividing the number of output points by 16/h.
(2) Processing time for the instruction (DUTY instruction) in END processing
Using the DUTY instruction increases the END processing time because the user timing clock (SM420 to SM424
and SM430 to SM434) specified with the instruction is turned on or off in END processing.
(3) Instruction execution time
The instruction execution time is a total of the time required for all instructions used in the program to be executed
and (a) and (B) described in the following page. For execution time of instructions, refer to the following.
MELSEC-Q/L Programming Manual (Common Instruction)
CPU module KM1 KM2
L02CPU 1.5 1.0
L26CPU-BT 1.5 1.0
CPU module
Processing time in END processing
When set to 1 When set to 5
L02CPU 6.9 [µs] 7.4 [µs]
L26CPU-BT 5.7 [µs] 6.1 [µs]
Stores the scan time of 1ms or less. (unit: s)
Stores the scan time. (in increments of 1ms)
SD520
SD524
SD526
Current value
Minimum value
Maximum value
SD521
SD525
SD527
Ex.
Ex.
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