Introduction; Overview Of The Module's Operation; Module Features - DirectLOGIC DL405 Manual

Introduction

Overview of the The DL405 Interrupt Input module (D4–INT) is
module's operation an 8-point isolated interrupt input module for
use with the DL405 family of products. The
module consumes 16 X input points and must
be installed in Slot 0, next to the CPU. You can
use two Interrupt modules, installed in Slots 0
and 1, if you are using a D4–440 CPU. (More
on this later.)
The Interrupt module is intended for applications
that have one or more high-priority events which
require immediate attention. That is, these are
events that cannot wait until the CPU has
finished it's normal program execution.
When this high priority event occurs, the
interrupt module sends an interrupt signal to the
CPU. Once the interrupt is received, the CPU
immediately suspends its routine scan cycle
and jumps to a subroutine that corresponds to
the particular interrupt input signal.
The following diagram shows a brief overview of this concept.

Module Features

This module has some great features that make interrupt processing easier.
P
U
Main Program
END Statement
Interrupt
Subroutine(s)
Interrupts are prioritized (lowest number takes priority)
Rising or Falling edge trigger
Selectable response delay (allows you to easily ignore false signals)
Module parameters are easily selected by setting dipswitches on the
back of the module
No complex programming, only simple ladder instructions are required
If you don't use all 8 points as interrupts, you can use the non-interrupt
points as regular discrete inputs.
I
N
T
1. Field device (event) triggers
an interrupt signal from the
interrupt module to the CPU.
3. CPU finishes the subroutine
execution and returns to the point
where it left in the normal
program execution.
2. CPU recognizes the interrupt, stops the
normal program execution, and jumps to
subroutine.
1 1
1