4 Data Exchange with the CPU Unit
4-2
CJ-series PROFIBUS Master Unit Operation Manual for NJ-series CPU Unit (W509)
4-1 Data Exchange with the CPU Unit
Data exchange between this Unit and the CPU Units uses the I/O port and memory for CJ-series Unit
allocated to the PROFIBUS Master Unit.
The CPU Unit and CJ-series PROFIBUS Master Unit exchange various types of information at each I/O
refresh via the memory for CJ-series Units within the CPU Unit.
From the user program, various types of information are exchanged using device variables and user-
defined variables. Device Variables are positioned internally in the CPU Bus Unit words allocated in
CIO and DM areas. User-defined variables are created by the user and can be allocated to specific
memory areas used for CJ-series Units allocated to slaves.
By using these variables, the user can program without the need to be aware of the configuration
of the memory used for CJ-series Units.
4-1-1 Data Flow
Access methods from
the user program
AT specification
destination
Data exchange timing Unit data type
Device variable for CJ-
series Unit
I/O port During I/O refresh Software switch
Status
User-defined variable Memory used for
CJ-series Unit
During I/O refresh Slave area I/O data
At I/O refresh after instruction execution Message send/receive data for
communications instructions
System-defined variable None During I/O refresh Unit Restart Flag, Communica-
tions Port Enabled Flags, etc.
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