GE 90-30/20/Micro manual Svcreq #8 Reset Watchdog Timer, Example

4

SVCREQ #8: Reset Watchdog Timer

Use SVCREQ function #8 to reset the watchdog timer during the sweep.

Note

Of the CPUs discussed in this manual, Service Request 8 is supported only by 90-30 CPUs, beginning with Release 8.0.

When the watchdog timer expires, the PLC shuts down without warning. This function allows the timer to keep going during a time-consuming task (for example, while waiting for a response from a communications line).

Caution

Be sure that restarting the watchdog timer does not adversely affect the controlled process.

This function has no associated parameter block; however, the programming software requires that an entry be made for PARM. Enter any appropriate reference here; it will not be used.

Example:

In the following example, when enabling output %Q0127 or input %I1476 or internal coil %M0010 is set, the watchdog timer is reset.

		_____
%Q0127
—— ———+—————————		SVC_—
		REQ
%I1476
—— ———	CONST —FNC
	0008
%M0010
—— ———+	%AI001—PARM
	_____

GFK-0467K Chapter 4 Series 90-30/20/Micro Instructions Set 4-149