Rockwell Automation 1772-L8_LW_LWP_LX_LXP,D17726.5.8 User Manual - Manual (Page 296)

Data Transfer File Instruction
Chapter 19
19-4
When the rung condition goes false, both the done and enable bits are reset
and the counter resets to position 001. If the rung was enabled for only
one scan, the done bit would come on during that scan and remain set for
one additional scan.
Distributed Complete Mode of Operation
In the distributed complete mode, the rate per scan is less than the file
length value and the entire file is transferred over several program scans.
For example, suppose you have a file that contains twelve words. If you
assign the value of 004 for the rate per scan that means that the instruction
executes four words per scan at a time. Therefore, the entire operation will
be completed in three consecutive scans.
For each true rung condition, the instruction is enabled. The number of
words equal to the rate per scan is operated upon during one scan. The
process is repeated over a number of consecutive scans until the entire file
has been transferred. Once the file instruction is enabled it remains
enabled for the number of scans necessary to complete the operation,
regardless of the rung condition.
At the time of completion, if the rung is true, the enable bit (bit 17) and the
done bit (bit 15) are both set. If the rung is false, the enable bit is reset
after the last group of words is operated upon. At the same time, the done
bit is set and stays set for one scan. During the next scan the done bit is
reset, and the counter is reset to position 001.
Incremental Mode of Operation
In the incremental mode, the rate per scan is equal to 0. This means that
upon each false-to-true transition one word is operated upon per scan, then
the counter increments to the next position. When the rung is true the
enable bit (bit 17) is set. After the last word in the file has been operated
upon, the done bit (bit 15) is set. When the rung goes false, the done and
enable bits are reset (after the last word has been operated upon), and the
counter is reset to position 001. If the rung remains true for more than one
scan, the operation does not repeat. The operation only occurs in the scan
in which the false-to-true transition occurs.