Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 294)

File Search and File Diagnostic Instructions
Chapter 17
17Ć2
The process continues until the end of the file is reached (position = file
length), at which time the done bit is set. The next false-true transition
starts the search again at the beginning of the file. If the last word of the
file contains a match, the position will equal file length, but the done bit
will not be set. On the next false-true transition, the counter will reset to
000 and the done bit is set. The done bit is reset when the rung goes false.
The search will begin again only after an additional false-true transition.
Instruction Overview:
Output instruction
Key Sequence: [FILE] 21
Counter is manipulated by instruction
Requires 4 user program words
Programming File Search Instruction
WARNING: The counter address specified for the File
Search instruction should be reserved for that instruction. Do
not manipulate the counter preset or accumulated values.
Inadvertent change to these values could result in hazardous or
unpredictable machine operation or run-time error. Damage to
equipment and/or personal injury could result.
To program a File Search instruction, press keys [FILE] 21. A display
represented by Figure 17.2 will appear.