Bradley Smoker PLC-5 Monitoring Selectable Timed Interrupts, Check for a non-zero value in S31

17-4Using Selectable Timed Interrupts

Monitoring Selectable Timed Interrupts

For example, you could enter a 7 in S:31 and a 15 in S:30. This causes the controller to execute ladder file 7 every 15 ms.

You can use only one STI at any one time. However, you can enable or disable the interrupt, change to a different interrupt file, or change the time between interrupts. Use ladder logic to change the values in word S:30 and word S:31 as needed.

ATTENTION	STI programs lengthen the program scan by an amount
	equal to the interrupt delay multiplied by the number of

times the interrupt occurs during a program scan.

	If you disable the STI through ladder logic (write a 0 to
IMPORTANT
	S:30), it could take the controller up to 100 ms to re-enable
	the STI. If you disable the STI (write a 0 to S:31), the
	controller uses the value in S:30 to determine how often to
	check for a non-zero value in S:31.

Use the controller status screen in your programming software to monitor STIs.

In this Field	Do the Following	Status
		File
Last scan	This field displays the time it took for the current or last	S:53
time	scan of the STI.
Maximum	This field displays the longest time that was ever	S:54
scan time	displayed in the Last scan field for the specific STI.
STI Overlap	This box is checked if an STI overlap occurs. This	S:10/2
	condition results if the interrupt interval you specify for
	the setpoint is shorter than the execution time of the
	STI program.

Publication 1785-UM012D-EN-P - July 2005