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

File Diagnostic Instruction

Chapter 4

47

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

010

0520

Execute Aux

Function

Function Number:

Data Addr:

Result Addr:

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

1 2 ... 19 20 21 22 23 24 25 26 27 28 29 30 31 32

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Rockwell-automation 1772-AF3,D17726.5.2 User Manual AUX FUNCT PROM User Manual Page 24