Справочник Пользователя для Mitsubishi Electronics FX5

5  SCAN MONITORING FUNCTION
5.1  Scan time monitoring time setting

This function detects CPU module hardware or program errors by monitoring the scan time. Using the watchdog timer, which 
is an internal timer in the CPU module, the following scans are monitored.
 • Initial scan (1st scan)
 • 2nd scan and after

Sets the scan time monitoring time.

Navigation window  [Parameter]  [FX5UCPU]  [CPU Parameter]  "RAS Setting"  "Scan Time Monitoring Time 
(WDT) Setting"

Window

Displayed items

Resets the watchdog timer when the END/FEND instruction is executed. When the CPU module operates normally and 
executes the END/FEND instruction within the watchdog timer setting, the time of the watchdog timer will not time up. If the 
END/FEND instruction cannot be executed within the watchdog timer setting due to increased program execution as a result 
of hardware error or interrupt in the CPU module, the time of the watchdog timer will time up.

The following precautions relate to the scan monitoring function.

The watchdog timer can be reset by executing the WDT instruction in a program. If the time of the watchdog timer is up while 
executing a program repeatedly by the FOR instruction and NEXT instruction, use the WDT instruction to reset the watchdog 
timer.

Initial Scan

Sets the scan-time monitoring time (WDT) for the initial scan (first 
scan).

10 to 2000 ms (10 ms units)

2000 ms

After 2nd Scan

Sets the scan-time monitoring time (WDT) for the second and later 
scans.

10 to 2000 ms (10 ms units)

200 ms

FOR K1000

WDT

NEXT

Program repeatedly executed

Resetting of the 
watchdog timer

Repeated 1,000 times

M0