Delta DVP-ES2/EX2/SS2/SA2/SX2/SE manual WDT, Wdtp 1 step

3. Instruction Set

API

07

Mnemonic		Function
WDT	P	Watchdog Timer Refresh

Controllers

ES2/EX2	SS2	SA2	SX2
		SE

OP

N/A

Descriptions

Program Steps

WDT, WDTP: 1 step

PULSE

16-bit

32-bit

ES2/EX2

SS2

SA2

SX2

ES2/EX2

SS2

SA2

SX2

ES2/EX2

SS2

SA2

SX2

SE

SE

SE

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

STEP0 WDT END(FEND)

T1 T2

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.

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