LSIS XBE-DC08A, Руководство пользователя, Страница: 131 / 1284

M
ain
Chapter 2 CPU Function
2-5
2.3 Self-Diagnosis Function
The Self-Diagnosis function is the function for the CPU part to diagnose the PLC system for defects. In case errors occur
during supplying the power to the PLC system or during operation, it detects errors to prevent malfunction of the system and
preventive maintenance.
2.3.1 Scan Watchdog timer (Scan Watchdog Timer)
The WDT (Watchdog Timer) is the function to detect the congestion of programs caused by PLC module’s hardware or
software.
(1) The Watchdog timer is the timer to be used to detect operation delay caused by the user program error. You
can set up the Watchdog timer’s detection time in XG5000’s basic parameters as below (Initial value: 500ms).
(2) The Watchdog timer monitors the scanning time during operation and when set detection time is exceeded, it
stops the PLC’s operations immediately. At this time, the output status is maintained or cleared based on the
details of ‘Output Hold when errors occur’.
(3) If it is expected that the Scan Watchdog Time is exceeded since it takes more time to process the specific part
of the user programs (in case of using FOR ~ NEXT command, CALL command, etc.), clear the Watchdog
timer through the ‘WDT’ command.
The ‘WDT’ command initializes the scan Watchdog time and restarts measuring time from 0.
1 스캔
스캔 END
WDT 설정값
WDT 카운트값
WDT 명령 실행
0 으로 초기화 됨
WDT 카운트값
(Example of initializing scan Watchdog timer through the WDT command )
(4) In case the Watchdog error occurs, you can clear the error by resupplying the power or converting the mode
into STOP.