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Rung
No.
1
2
3
116
020
4
G
<
000
056
Examine Input
Status Word
Accumulated Value
However, in some applications, one or both preset words must be
used. Here, the complication involving the output image table word
is readily apparent: it must be used to serve multiple purposes; not
only will this word send the output control word, it is also needed to
send one or both preset words to the module. The use of this word
for more than one purpose is termed multiplexing. For multiplexing,
program manipulation and coordination of the control of the output
image table word are necessary. Sections titled Multiplexing and
Example Program - Single Transfer describe multiplexing for
single transfer communication.
Example Rungs No Preset Words Used
Figure 5.5 illustrates a typical example in which bidirectional single
transfer occurs, assuming that no preset words are used. This
example assumes the module placement shown in Figure 5.4.
There is no manipulation of intermediate storage words when only
the output control word is needed. Thus, in this instance, the bits in
the output image table word corresponding to the module are set
directly to determine the module's control function. In the example
of Figure 5.5, rungs 1-3 turn on various bits in the output word. Bits
are 0 unless set to 1 by a program instruction. Here, it is assumed
that no other use is made of word 016.
Figure 5.5
Example Rungs Single Transfer (No Preset Words used)
Single Transfer Programming
01617
01613
01607
Publication 1771 UM006B-EN-P - June 2002
5–7
Set Control
Word Bits as
Desired, Word
016 Used
Directly For
Control Word
Function
15956
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