Rockwell Automation 1772-AF3,D17726.5.2 User Manual AUX FUNCT PROM - Manual (Page 24)

File Diagnostic Instruction
Chapter 4
4Ć7
You enable the file diagnostic instruction in program logic using a separate rung
that precedes the instruction (Figure 4.8). Address an output or latched output
instruction to bit 17 of the file diagnostic instruction’s result address, 0520/17.
Program the rung’s input conditions to cycle a false-to-true transition of the
output instruction. This initiates a search for the next mismatched word in the
file in accordance with your application.
Figure 4.8
Example Minimum Logic
17
010 0520
Execute Aux
Function
Function Number:
Data Addr:
Result Addr: 20
0500
0520
Control bits of the file diagnostic instruction are located in the first result word,
bits 17 thru 14 as follows.
Bit: 17
Function: Enable (EN)
Description: Your program logic must cause a false-to-true transition of the
enable bit for the instruction to operate. Program logic must reset then set the
enable bit before the instruction can search the file for the next mismatch. This
is the only bit that your program logic should manipulate.
Bit: 16
Function: Last State (LS)
Description: The instruction toggles this bit from off to on to off each time the
instruction is enabled and then reset after each match. The last state bit is used
by the instruction to remember the status of the enable bit in the previous scan.
This prevents the instruction from executing the next search until the enable bit
undergoes another false-to-true transition.
Enabling the Instruction
Function of Control Bits