Installation manual

Publication 1747-RM001G-EN-P - November 2008
Understanding Interrupt Routines 11-27
I/O Interrupt Overview (ISR)
This function allows a specialty I/O module to interrupt the normal processor
operating cycle in order to scan a specified subroutine file. Interrupt operation
for a specific module is described in the user’s manual for the module.
Not all specialty I/O modules are capable of generating I/O interrupts. Refer
to the user manual of the specific specialty I/O module to see if it supports
this feature. For example, you cannot use a standard discrete I/O module to
accomplish an I/O event-driven interrupt.
This section describes:
• I/O operation.
• I/O interrupt parameters.
• IID and IIE instructions.
• RPI instruction.
• INT instruction.
Basic Programming Procedure for the I/O Interrupt Function
• When you are configuring the specialty I/O module slot with the
programming device, make sure you program the “ISR” (interrupt
subroutine) program file number (range 3 to 255) that you want the
processor to execute when the module generates an interrupt. Specialty
I/O modules that create interrupts should be configured in the lowest
numbered I/O slots.
• Create the subroutine file that you have specified as the ISR number in
the I/O module slot configuration.
Operation
When you restore your program and enter the REM Run mode, the I/O
interrupt begins operation as follows.
1. The specialty I/O module determines that it needs servicing and
generates an interrupt request to the SLC processor.
2. The processor is interrupted from what it is doing, and the specified
interrupt subroutine file (ISR) is scanned.
3. When the ISR scan is completed, the specialty I/O module is notified.
This informs the specialty I/O module that it is allowed to generate a
new interrupt.
4. The processor resumes normal operation from where it left off.
Fixed SLC
5/01
SLC
5/02
SLC
5/03
SLC
5/04
SLC
5/05
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