Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 216)

Chapter
12
12Ć1
Data Transfer File Instructions
This chapter introduces concepts in two major areas:
Files
Data monitor mode
Later chapters of this manual are written with the assumption that the
concepts and terms covered in this chapter have been thoroughly learned.
In particular, do not proceed into Chapters 13-17, File, Sequencer, and
Shift Register instructions, until this chapter is completely understood.
The definition of a file, the pictorial representation of the File instruction
and the modes of File instruction operation are covered in this chapter. The
illustrations help to describe these concepts.
A file is a group of consecutive data table words used to store information .
It is defined by a counter and the starting word address of the file. The
counter has two functions:
It defines the number of words in the file (file length) with its preset
value.
It points to a particular word in the file (position) with its accumulated
value.
The counter address is also referred to as the instruction address. It is the
address used by the processor to search for the instruction. The words in
the file must be located one after the other. A file can be from one to a
maximum of 999 words in length. The first word in a file is defined as
word 1 and is located at position 001.
The structure of a file is presented in Figure 12.1. This figure illustrates a
12-word file starting at word address 600
8
. The counter (at address 200
8
)
has an accumulated value of 005. It points to the fifth word in the file,
word address 604
8
. This word will be either the source or destination of the
data that is currently being operated upon by the File instruction.
12.0
General
12.1
File Concepts
12.1.1
File Definition