Rockwell Automation 1771-IJ_IK IK ENCODER/COUNTER MODULES - Manual (Page 37)

5–7 Single Transfer Programming
Publication 1771ĆUM006B-EN-P - June 2002
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 Ć 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 Ć Single Transfer (No Preset Words used)
01617
Rung
1
2
No.
3
4
01613
01607
116
000
020
056
Set Control
Word Bits as
Desired, Word
016 Used
Directly For
Control Word
Function
Examine Input
Status Word
Accumulated Value
15956
< G