10 - 3
10. OTHER FUNCTIONS
(2) Setting the constant scan time
(a) The setting is made in "PC RAS" in the parameter mode of GPP function.
• When performing the constant scan, set the constant scan time.
• When not performing the constant scan, leave the field blank.
Example: When setting 100ms to "Constant scan"
(b) Set constant scan time that is longer than the maximum scan time of the
sequence program. If the scan time of the sequence program is longer than the
set value for constant scan time, the QnACPU detects an error code (SD0 =
5010), and the sequence program is performed in the own scan time, ignoring
the constant scan time setting.
Make sure that the constant scan time setting is shorter than the set time for
WDT (Watchdog timer). If it is longer than the set time for WDT, the QnACPU
detects a WDT error and the program execution is stopped.
Set the constant scan time within the following range.
(c) Sequence program processing is suspended in the wait time between the END
processing of the sequence program and the start of the next scan.
However, if an interrupt factor occurs after the execution of END processing, or if
there is a low-speed execution type program, the interrupt program or the low-
speed execution type program is performed.
Setting time for WDT Setting time for constant scan Maximum scan time of sequence program
Fig. 10.2 Operation when scan time is longer than constant scan setting time
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