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MELSEC-Q
4 SEQUENCE PROGRAM CONFIGURATION AND EXECUTION
CONDITIONS
(4) Initial scan time
(a) This is the execution time period for initial execution type programs.
If multiple initial execution type programs are executed, it is the execution
time period in which all those programs are executed.
When an interrupt program/fixed scan execution type program is executed
while an initial execution type program is running, the execution time of the
interrupt program/fixed scan execution type program will be added to the
initial execution type program.
(b) The High Performance model QCPU measures the initial scan time and
stores the result in special registers (SD522, SD523). 1
The initial scan time can be checked by monitoring the SD522 and SD523
special registers.
Stores less than 1 ms initial scan time (unit s)
Stores the initial scan time in 1 ms units.
SD522
SD523
If the SD522 value is 3, and the SD523 value is 400, the initial scan time is
3.4 ms.
POINT
1: The accuracy of the initial scan time stored at the special registers is ± 0.1 ms.
The initial scan time count will continue even if a watchdog time reset
instruction (WDT) is executed at the sequence program.
(5) Initial execution monitor time
(a) The execution period of the initial execution type program can be monitored
by this timer. The default value is not set.
When monitoring the execution time of the initial execution type program,
designate the initial execution monitor time within the range of 10 to 2000
ms range at the "PLC RAS" tab screen in the “(PLC) Parameter" dialog box.
(Setting unit: 10 ms)
(b) The low speed execution type program is executed after the execution of
the initial execution type program is completed.
To use the low speed execution type program, specify the time that is
longer than the sum of the initial scan time and the execution time of the
low speed execution type program.
(c) When the initial scan time exceeds the set initial execution monitor time,
"WDT ERROR (error code: 5000)" occurs, and High Performance model
QCPU operation is stopped.
POINT
When the initial execution monitor time is designated, there will be a 10 ms error in
the count value.
Therefore, a monitor time setting (t) of 10 ms will result in a "WDT ERROR" when
the initial scan time is in the range 10 ms < t < 20 ms.
