System Power, Expansion and I/O Allocations

B-112 Programmable Controller

CJ1

I/O Allocations

J Overview

In CJ1 Series PLCs, I/O memory is allocated based on

the following: Basic I/O are automatically assigned words

based on position in the rack. In contrast, for Communica-

tions and Bus I/O, the user assigns the word allocations

within set ranges.

J Allocations to Basic I/O

Module Groups

Allocated words in the CIO Area: CIO 0000 to CIO 0079

Basic I/O Modules can be mounted to the CPU Rack and to

the Expansion Racks.

CPU Rack Allocations

Basic I/O Modules on the CPU Rack are allocated words

left to right (i.e., from the module nearest the CPU) starting

from CIO 0000. Modules are allocated as many words as

required in word units. Words can be reserved using

CX-Programmer Software.

Up to 10 modules

can be mounted.

CPU Rack

CIO

0000

CPU Rack

IN

16

CIO

0000

IN

16

CIO

0001

IN

32

CIO

0002

to

0003

OUT

32

CIO

0004

to

0005

OUT

64

CIO

0006

to

0009

An example of : words allocated from the left.

Modules with between 1 and 16 I/O points are allocated 1

word (16 bits), and modules having between 17 and 32 I/O

points are allocated 2 words (32 bits). For example, 8-point

Relay Modules are allocated 1 word, with bits 00 to 07

actually allocated to the I/O points.

Allocations to Expansion Racks

I/O allocation to Basic I/O Modules continues from the CPU

Rack to the Expansion Racks. Words are allocated from

left to right, and each module is allocated as many words

as it requires in word units— just like modules in the CPU

Rack. A Rack’s first word setting can be changed to any

word from CIO 0000 to CIO 9999.

CPU Rack

Expansion Rack

Expansion Rack

Words

allocated

in order

from Rack

nearest

CPU Rack.

Words allocated from the left.

Words allocated from the left.

0000

CH

CIO

0000