Rockwell Automation D64046.5.1 U MNL WIN DDMC - Manual (Page 19)

Chapter 1
Understanding How a DDMC32 System Works
1-7
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
outputs (real or logical)
lube level sensors
alarms
fault bits set by another device or by ladder logic
any valid bit address
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)
3
ASSEMBLY
MACHINE
N27:0
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.
Understanding the DFA
Instruction