Rockwell Automation D64046.5.1 U MNL WIN DDMC - Manual (Page 76)

Chapter 5
Configuring DFA Instructions
5-2
The Diagnostic Fault Annunciator (DFA) instruction is a monitoring only
instruction; that is, it monitors inputs you define, but it cannot control
outputs. Valid inputs can be:
storage points, such as binary bits
counter / timer done bits
discrete outputs (real or logical)
any valid bit address
fault bits set by another device (like an IMC motion controller) or by
ladder logic
The following figure shows a DFA instruction in a ladder program.
A DFA Instruction (PLC-5/250)
DFA
DIAGNOSTIC FAULT ANNUNCIATOR
Control File
No. of I/O
Program file number
(EN)
(ER)
1
ASSEMBLY
MACHINE
1N10:0
16
Msg Control Block 0MSG0:0
If you currently have diagnostics programmed in ladder logic, you can use
the DFA instruction to generate messages when a fault occurs. In addition,
you can create other types of operational and diagnostic messages with the
DFA instruction, such as tool change messages and operating instructions.
Once you have determined where you want to apply the DFA instruction,
you can enter it into your ladder program and configure the instruction.
You perform the following tasks to program the DFA instruction:
download the DFA CAR
enter the DFA instruction
enter the configuration information
enter I/O information
Diagnostic Fault
Annunciator Overview
Programming the DFA
Instruction