2 Basic System Configuration and Devices
2-10
CJ2 CPU Unit Hardware User’s Manual
A maximum of 10 Units can be connected to the CPU Rack for a CJ2 CPU Unit or to an Expansion
Rack. There are no restrictions in the number of each model of Unit based on location.
Note A fatal error will occur and the CPU Unit will not operate if more than the allowable number of Units is con-
nected to a CJ2 CPU Rack or to an Expansion Rack.
The Configuration Units with which the CJ2 CPU Unit can exchange data are classified into three
groups. The number of Units that can be mounted depends on the type of Unit.
2-1-4 Configuration Units
Maximum Number of Units
Models of Configuration Units
Units Description
Unit identifica-
tion method
Number of
mountable Units
Basic I/O Units Basic I/O Units are used for discrete inputs and
outputs.
Identified by the
CPU Unit accord-
ing to mounting
position.
No limit
Special I/O Units Special I/O Units are more advanced than Basic
I/O Units. They support functions other than dis-
crete inputs and outputs.
Examples:
Analog I/O Units and High-speed Counter Units
Special I/O Units have a smaller area for
exchanging data with the CPU Unit than CPU
Bus Units (including Network Communications
Units).
Identified by the
CPU Unit using
unit numbers 0 to
95 set with the
rotary switches on
the front panel of
the Unit.
Up to 96 Special
I/O Units can be
mounted.
(Depending on the
model, 1 to 4 unit
numbers are used
for one Unit.)
CPU Bus Unit CPU Units are advanced units that exchange
data with the CPU Unit via the CPU bus.
Examples:
Network Communications Units and Serial Com-
munications Units
CPU Bus Units have a larger area for exchang-
ing data with the CPU Unit than Special I/O
Units.
Identified by the
CPU Unit using
unit number 0 to F
set with the rotary
switch on the front
panel of the Unit.
Up to 15 CPU Bus
Units can be
mounted.
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