Delta AH500 - Explanation of Other Instructions

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Chapter 6 Applied Instructions

6-429

6.20.2 Explanation of Other Instructions

API

Instruction code Operand

Function

1900 WDT P

─

Watchdog timer

Pulse instruction 16-bit instruction (1 step)

32-bit instruction

─

AH500

─

Symbol:

Explanation:

1. In the AH500 series PLC, there is a watchdog timer which is used to monitor the operation of

the system.

2. The instruction WDT is used to reset the watchdog timer in the PLC. If the program scanning

time exceeds 200 milliseconds, the error LED indicator is ON, and the PLC stops running.

3. The particular point when the watchdog timer acts:

 The system is abnormal.

 The execution of the program takes much time, and therefore the scam time is larger

than the setting value of the watchdog timer. There are two way users can use to improve

the situation.

1. Using the instruction WDT

STEP0

END

WDT

2. Please refer to ISPSoft User Manual for more information about changing the

setting value of the watchdog timer.

Example:

Suppose the program scanning time is 300 milliseconds. After the program is divided into two parts,

and the instruction WDT is inserted between these two parts, the time it takes to scan either the first

part of the program or the second part of the program is less than 200 milliseconds.

Additional remark:

Please refer to ISPSoft User Manual for more information related to the setting of the watchdog

timer.

Other manuals for Delta AH500