Data Transfer File Instructions
Chapter 12
128
Figure 12.7
Distributed
Complete Mode Operation
Data Table
Scan #1
Rates Per Scan = 005
File is operated upon over 3 scans.
Operation goes to completion after a single falseto
true transition of the rung condition.
512
516
517
527
523
524
Scan #2
Scan #3
Scan #3
Scan #2
Scan #1
5 W
ords
5 W
ords
Remaining
4 W
ords
The File instruction, once enabled, remains enabled for the number of
scans necessary to complete the operation. The rung could become
repeatedly false and true during this time without interrupting the
instruction.
NOTE: It is important that the user program not make use of the results of
a File instruction operating in the distributed complete mode until the done
bit is set. At completion, the rung containing the instruction could either be
true or false. If the rung is true at completion, the enable and done bits are
both 1.
They are reset to zero and the counter is reset to position 001 when the
rung goes false. However, if the rung is false at completion, the enable bit
is reset to zero after the last group of words is operated upon. At the same
time, the done bit comes on and stays on for one scan. The done bit is
reset to zero and the counter is reset to position 001 in the next scan. The
operation of the status bits is shown in Figure 12.8 for the two cases: false
at completion and true at completion.
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