Allen-Bradley 1770-M11 User Manual download pdf (Page 8)

8 SLC 500™ Chassis–Based Processors

Publication 1747-2.39

Interrupt Subroutines

The following interrupt subroutines allow you to provide

predetermined responses to special events in an application.

Selectable Timed Interrupt

This function allows you to interrupt the scan of the processor

automatically, on a periodic basis, in order to scan a specified

subroutine file. When using an SLC 5/02 processor, the

Selectable Timed Interrupt (STI) timebase can be adjusted in 10

ms increments. The timebase for the SLC 5/03, SLC 5/04, and

SLC 5/05 processors can be adjusted in 1 ms increments. The

SLC 5/03 processor begins at 2 ms STI, and the SLC 5/04 and

SLC 5/05 processors begin at 1 ms STI.

Discrete Input Interrupt

Use the Discrete Input Interrupt (DII) for high–speed processing

applications or any application that needs to respond to an event

quickly. This function allows the processor to execute a ladder

subroutine when the input bit pattern of a discrete I/O card

matches a compare value that you programmed. The discrete

input interrupt is examined every 100 µs asynchronous to the

ladder program scan. You may also specify the number of counts

(matches) to occur before subroutine execution.

I/O Event Interrupt

This function allows the 1746–BAS (BASIC) module to interrupt

the normal processor operating cycle in order to scan a specified

subroutine file. Use this interrupt with SLC 5/02, SLC 5/03, SLC

5/04, and SLC 5/05 processors.

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Allen-Bradley 1770-M11 User Manual Page 8