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CompoBus/S I/O Link Units Section 7-6
I/O Allocation
I/O words are allocated to the CompoBus/S I/O Link Unit in the same way as
to other Expansion Units and Expansion I/O Units, i.e., the next available input
and output words are allocated. As shown below, when “m” is the last allo-
cated input word and “n” is the last allocated output word, the CompoBus/S I/
O Link Unit is allocated “m+1” as its input word and “n+1” as its output word.
In the following example, a CompoBus/S I/O Link Unit is connected as the first
Unit after the CP1H CPU Unit.
The input word (m+1) contains the 8 bits of data from the Master Unit and two
CompoBus/S communications flags.
Write the data to be transmitted to the Master Unit in the output word (n+1).
Note (1) The 8 bits of I/O data are not always transmitted simultaneously. In other
words, 8 bits of data transmitted from the Master CPU Unit at the same
time will not always reach the Slave CPU Unit simultaneously, and 8 bits
of data transmitted from the Slave CPU Unit at the same time will not al-
ways reach the Master CPU Unit simultaneously.
When the 8 bits of input data must be read together, modify the ladder
program in the CPU Unit receiving the data. For example, read the input
data twice in succession and accept the data only when the two values
match.
(2) Unused bits in the CompoBus/S I/O Link Unit’s output word can be used
as work bits, but unused bits in the output slaves cannot be used as work
bits.
Word m+1
CompoBus/S I/O Link Uni
8 inputs
8 outputs
Word n+1
CP1H
CPU Unit
CompoBus/S
I/O LInk Unit
Input words
Output words
CIO 0
CIO 1
CIO 100
CIO 101
CIO 2
CIO 102
Word m+1
15 00
070809
CompoBus/S Communications Error Flag
0: Normal; 1: Error
CompoBus/S Communication Status Flag
0: Stopped; 1: Communicating
Data from the Master Unit
Word n+1
15 00
07
Data to be transferred to the Master Unit
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