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MELSEC-Q
18 PROCESSING TIME FOR MULTIPLE PLC SYSTEM HIGH
PERFORMANCE MODEL QCPUs
18 PROCESSING TIME FOR MULTIPLE PLC SYSTEM HIGH
PERFORMANCE MODEL QCPUs
18.1 Concept behind CPU Scanning Time
The concept behind multiple PLC system scanning time is the same as the single CPU
system.
See Section 11.1 for details of the scan time concept.
This chapter provides explanations on the factors to be added to the scan time
calculated as explained in Section 11.1 and the method of calculating processing time
when configuring multiple PLC systems.
(1) I/O refresh time
Input refresh time is calculated in accordance with the equation explained in
Section 11.1.
The I/O refresh time for the following values only are prolonged when bus access
overlaps with other PLCs.
(input points + output points)
(Prolonged time) =
16
N3 (number of other PLCs) ( s)
Use the following values for N3
N3
CPU type
Systems with only a main base
unit
Systems that include additional
base units
Q02CPU
Q02HCPU, Q06HCPU
Q12HCPU, Q25HCPU
8.7
s 21 s
(2) Total value of command execution time
Refer to the following manual for details on the processing time of special
multiple PLC commands, and the processing time for commands that have
different processing times with multiple PLC systems.
• QCPU (Q mode)/QnACPU Programming Manual (Common Instructions)
(3) END process
The following tables shows the END processing time.
CPU type END processing time
Q02CPU 0.42 ms
Q02HCPU, Q06HHCPU, Q12HCPU, Q25HCPU 0.19 ms
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