8 I/O Allocations and Unit Settings
8-14
CJ2 CPU Unit Software User’s Manual
In the CJ-series PLCs, the first word allocated to each Rack can be set with the CX-Programmer’s I/O
table edit operation. For example, the CPU Rack can be set to be allocated words starting with CIO
0000; the next Rack, words starting with CIO 0100; the next Rack, words starting with CIO 0200; etc.
This can make it easier to check word allocations to Units without calculating all the way from the CPU
Rack.
z Word Allocations
For Racks in which the first word address has been set, words are allocated to Units in the order that
the Units are mounted (from left to right) beginning with the specified first word. Words are not allo-
cated to empty slots.
For Racks in which the first word address has not been set, words are allocated in rack-number
order (lowest to highest) continuing from the last word allocated to the previous rack and starting
with CIO 0000 on the first Rack for which the first word is not set.
Example: Setting the First Words for Racks
Allocating First Words to Racks
0 1 2 3 4
0 1 2 3
0 1 2 3 4
CIO
0100
CIO
0103
CIO
0122
CIO
0002
First Rack word set to CIO 0100.
First Rack word not set ∗
CIO
0101
CIO
0102
CIO
0120
CIO
0121
CIO
0000
CIO
0001
CIO
0104
CIO
0123
CIO
0003
CIO
0004
0 1 2 3 4
CIO
0142
CIO
0140
CIO
0141
CIO
0143
CIO
0144
∗ (automatic allocation from CIO 0000).
CPU Rack
(Rack 0)
Rack 1
CPU UNIT
Power Supply Unit
I/O Control Unit
Power Supply Unit
I/O Interface Unit
First Rack word set to CIO 0120.
Rack 2
Power Supply Unit
I/O Interface Unit
First Rack word set to CIO 0140.
Power Supply Unit
I/O Interface Unit
Rack 3
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