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(1) How to check scan time
The CPU module measures current, minimum, and maximum values of the scan time.
The scan time can be checked by monitoring the special register (SD520, SD521, and SD524 to SD527).
Accuracy of each stored scan time is 0.1ms.
If the stored values in SD520 and SD521 are 3 and 400 respectively, the scan time is 3.4ms.
10.1.2 Time required for each processing included in scan time
This section describes how to calculate the processing and execution time described in Section 10.1.1.
(1) I/O refresh time
The I/O refresh time is time required for refreshing I/O data to/from the following modules mounted on
the main base unit and extension base units.
• Input module
• Output module
• Intelligent function module
Calculation method
Use the following expression to calculate the I/O refresh time.
(I/O refresh time) = (number of input points/16) N1 + (number of output points/16) N2
For N1 and N2, refer to
Table10.1.
Figure 10.2 Scan time storage location
Table10.1 I/O refresh time
CPU module
Q3 B, Q3 SB, Q3 RB, Q3 DB Q5 B, Q6 B, Q6 RB
N1 N2 N1 N2
Q00UJCPU, Q00UCPU, Q01UCPU
1.8 s 1.0 s 2.6 s 1.9 s
Q02UCPU
1.5 s 1.1 s 2.4 s 1.9 s
Q03UDCPU, Q04UDHCPU,
Q06UDHCPU, Q10UDHCPU,
Q13UDHCPU, Q20UDHCPU,
Q26UDHCPU, Q03UDECPU,
Q04UDEHCPU, Q06UDEHCPU,
Q10UDEHCPU, Q13UDEHCPU,
Q20UDEHCPU, Q26UDEHCPU
1.5 s 1.0 s 2.3 s 1.8 s
Stores the scan time of 1ms or less (unit: s).
Stores the scan time. (unit: ms).
SD520
SD524
SD526
Current value
Minimum value
Maximum value
SD521
SD525
SD527
Example