Rockwell Automation 1772-AF3,D17726.5.2 User Manual AUX FUNCT PROM - Manual (Page 4)

Introduction
Chapter 1
1Ć2
This publication shows you how to install and use the AF3 PROM in your
Mini-PLC-2/15 controller.
We assume that you are familiar with programming and operation of the
Mini-PLC-2/15 controller and the Industrial Terminal (cat. no. 1770-T3). We
also assume that you are familiar with files and file instructions.
WARNING: : Use only Allen-Bradley authorized programming
devices to program Allen-Bradley programmable controllers.
Using unauthorized programming devices may result in
unexpected operation, possibly causing equipment damage
and/or injury to personnel.
Programs for machine diagnostics minimize machine downtime and
maintenance time. Troubleshooting time is also reduced by isolating failed
machine components and devices. In cases where devices are direct inputs to
the PC, such as mechanical components, diagnostic programs can be used to
isolate problem areas by monitoring various critical machine or process
parameters. Diagnostic routines can even warn of potential failures so that
preventive maintenance can be performed at a convenient or scheduled time
before the failure occurs. Machine failures can also be recorded by the PC to
provide historical failure/reliability trend information.
All machine failures and malfunctions detected by the PC can be displayed
directly by several methods. Fault code numbers related to specific faults can
be displayed on an LED display, or alphanumeric messages can be displayed on
a CRT or printer to describe the faulted device or malfunction.
There are several methods commonly used to implement machine diagnostics.
One method is referred to as extended data comparison (EDC). This diagnostic
method is a useful technique for automatically detecting an out of sequence or
faulted I/O device. EDC can be summarized as follows: At each step in a
particular sequence or operation, a word containing the actual I/O status is
compared to a desired or standard I/O status word. If the machine or process is
operating properly, the bit pattern of the actual I/O word will be identical to the
bit pattern of the desired I/O status word.
Should an input fail, or be out of sequence, the bit patterns would differ, and
your program would initiate a routine that would determine which bit of the
input word represented a faulted input. the basic EDC concept is normally
expanded to include a group or file of input words and a corresponding file of
desired standard words. By comparison with a standard, each input is checked
Purpose of This Publication
Audience
Programs fo Implementing
Machine Diagnostics
Extended Data Comparison