Installation manual

Publication 1747-RM001G-EN-P - November 2008
11-18 Understanding Interrupt Routines
Discrete Input Interrupt
Overview
Use the Discrete Input Interrupt (DII) for high-speed processing applications
or any application that needs to respond to an event quickly. This instruction
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 status file contains six bit values and six word values used to program and
monitor the DII function. The DII does not require ladder logic instructions
for configuration. You program the DII to examine the input bit pattern of the
first bits of any single I/O slot, which contains any discrete input card (such as
IG16, IV16, IB8, IB32). When the input bit pattern matches the compare
value, the accumulator is incremented. The DII accumulator counts to the
preset value and, once the interrupt is generated, it immediately wraps around
and begins counting again at zero.
While scanning the DII subroutine, you can reconfigure the DII to look for an
entirely different event. This facilitates DII sequencing. The DII can be
programmed to compare each input point to either a high (1) or low (0) state.
The accumulator is incremented on the input transition that causes the input
points to match the compare value.
IIM or IOM instructions are needed in the DII subroutine if your application
requires immediate update of input or output points. End the DII subroutine
with an RET instruction.
Basic Programming Procedure for the DII Function
To use the DII function with your main program file:
1. Create a subroutine file (range is from 3 to 255) and enter the desired
ladder rungs. This is your DII subroutine file.
(Project Tree - Controller Folder - Processor Status File - DII Tab)
2. Enter the Input Slot number (word S:47).
3. Enter the Bit Mask (word S:48). Valid Bit Masks range from 0 to 255.
4. Enter the Compare Value (word S:49). Valid Compare Values range
from 0 to 255.
5. Enter the Preset Value (word S:50). Valid Preset Values range from 0 to
32,767.
6. Enter the DII subroutine File Number in word S:46 of the status file.
(See page B-55.) A zero value disables the DII function.
Fixed SLC
5/01
SLC
5/02
SLC
5/03
SLC
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SLC
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