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3.3 Settings for Creation and Execution of Multiple Sequence Programs
3.3.2 Scan execution type program
3
SEQUENCE PROGRAM CONFIGURATION AND
EXECUTION CONDITIONS
2) Accuracy and measurement of scan time
The accuracy of each scan time stored into the special registers is 0.1ms.
Even if the watchdog timer reset instruction (WDT) is executed in a sequence
program, the measurement of each scan time is continued.
3) Execution of multiple scan execution type programs
When multiple scan execution type programs are executed, the scan
execution type program execution time is the time taken until the execution of
all scan execution type programs is completed.
When an interrupt program/fixed scan execution type program is executed,
the interrupt program/fixed scan execution type program execution time is
added to the scan time.
(b) END processing
When all scan execution type programs are executed, an END processing is
performed and the first scan execution type program is executed again.
By placing the COM instruction at the end of each scan execution type program,
the END processing (network refresh) can be performed for each program.
(c) WDT (Watchdog timer)
The watchdog timer (hereafter abbreviated to the WDT) watches the scan time.
The default value is 200ms.
1) WDT error
A WDT error is 10ms.
When the WDT (t) is set to 10ms, a "WDT ERROR" occurs within a scan time
range of 10ms<t<20ms.
2) WDT setting
The WDT setting can be changed in the PLC RAS setting of the PLC
parameter dialog box.
(
(3)(b) in this section)
Remark
The execution time of the program being executed can be checked in the program
list monitor of GX Developer.(
(d) Scan execution type program can be repeated at fixed intervals
When the constant scan function (
Section 6.2) is used, a scan execution
type program can be executed repeatedly at fixed intervals.
When the constant scan is set, a scan execution type program is executed at
intervals of the preset constant scan time.
