Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 217)

Data Transfer File Instructions
Chapter 12
12Ć2
Figure 12.1
File Structure
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Counter Addr: 200
Starting Address of File: 600
File Length - 012 = Preset Value
Position = 005 = Accumulated Value
Position Word Address
001
005
012
600
604
613
File Length =
12 Words
Current
Word Being
Operated Upon
(5th Word = Word 604
8
)
Although files can be located anywhere within the data table, they usually
should be located after the last timer/counter preset area. Timer/Counter
accumulated values and preset values are 100
8
apart. Files are made up
of consecutive words. Therefore, a file which begins in a timer/counter
accumulated area could continue on into the preset area and write over the
preset values found there. A file should not be inadvertently programmed
to overlap or be totally contained within another. Care should be taken in
assigning file areas to avoid unintentionally altering the contents of one file
by the operation of another.
To avoid programming errors of this kind,, data table documentation
sheets, described in Chapter 3, should be used. These are tally sheets on
which all data table words are logged as they are assigned and/or reserved
for I/O devices, timers, counters, bit/word storage and file storage.
Documentation of this kind should be included as a necessary part of the
control system documentation.
File instructions are displayed in block format. Figure 12.2 illustrates an
example file instruction. Each address or data entry required is identified
within the block and defined beneath it.
12.1.2
File Planning
12.1.3
File Instructions