Delta DVP-ES2 - Manual (Page 171)

3 . I n s t r u c t i o n S e t
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API Mnemonic Function
07 WDT P Watchdog Timer Refresh
Controllers
ES2/EX2 SS2
SA2
SE
SX2
OP Descriptions Program Steps
N/A WDT, WDTP: 1 step
PULSE 16-bit 32-bit
ES2/EX2 SS2
SA2
SE
SX2 ES2/EX2 SS2
SA2
SE
SX2 ES2/EX2 SS2
SA2
SE
SX2
Explanations:
1. WDT instruction can be used to reset the Watch Dog Timer. If the PLC scan time (from
address 0 to END or FEND instruction) is more than 200ms, the ERROR LED will flash. In
this case, users have to turn the power OFF and then ON to clear the fault. PLC will
determine the status of RUN/STOP according to RUN/STOP switch. If there is no
RUN/STOP switch, PLC will return to STOP status automatically.
2. Time to use WDT:
a) When an error occurs in the PLC system.
b) When the scan time of the program exceeds the WDT value in D1000. It can be modified by
using the following two methods.
i. Use WDT instruction
T1 T2
STEP0 END(FEND)
WDT
ii. Use the set value in D1000 (Default: 200ms) to change the time for watchdog.
Points to note:
1. When the WDT instruction is used it will operate on every program scan as long as its input
condition has been made. To force the WDT instruction to operate for only ONE scan,
users have to use the pulse (P) format of the WDT instruction, i.e. WDTP.
2. The watchdog timer has a default setting of 200ms. This time limit can be customized to
users requirement by editing the content in D1000, the wathdog timer register.