Omron SYSMAC CJ1W-EIP21, Operation Manuals

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A-19
Appendices
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
A-4 V
ariab
le Mem
o
ry
Allocation
Meth
od
s
App
A-4-2 Impor
tant C
ase Examples
When you exchange structure variable data between an NJ-series CPU Unit and a remote device, you
must align the memory configuration of the structure variable members with those of the remote device.
This section describes what to do in either the NJ-series CPU Unit or in the remote device.
Additional Information
This is not necessary when you exchange data between NJ-series CPU Units.
There are two methods that you can use to align the memory configuration with a remote device. For
example, the differences in the memory configuration for structure variables between an NJ-series
CPU Unit and a CJ-series CPU Unit are shown below.
This section describes how to align the memory configuration for these Units.

Method 1: Changing the Memory Configuration of the Structure Variable in
the NJ-series CPU Unit
With an NJ-series CPU Unit, you can specify member offsets to change the memory configuration of
the members of a structure variable. You can change the memory configuration of the members of a
structure variable in the NJ-series CPU Unit so that it is the same as the memory configuration in a
remote device that the CPU Unit will communicate with. Specify the member offsets for a structure
variable when you register the structure data type.
To communicate with a CJ-series CPU Unit, you can set the offset type to CJ to automatically use
the CJ-series memory structure. You can set the offset type to User to freely set your own offsets.
A-4-2 Important Case Examples
Aligning the Memory Configuration with a Remote Device
Data Type Definitions
Bytes
NJ-series Structure Variable NJ_X
First byte
First byte + 4
First byte + 6
First byte + 8
Variable Table
a
b
c
Name
Structure Y
a
b
c
Data type
STRUCT
DINT
INT
DINT
Name
Variable NJ_X
Data type
Structure Y
a
b
Not used.
c
Data Type Definitions
Name
Structure Y
a
b
c
Data type
STRUCT
DINT
INT
DINT
Bytes
CJ-series Structure Variable CJ_X
First byte
First byte + 4
First byte + 6
Variable Table
Name
Variable CJ_X
Data type
Structure Y