Input And Output Data - Omron CJ1W-PRT21 Operation Manual

Input and Output Data

4-1

Input and Output Data

Definitions
Slave INPUT Data
Slave OUTPUT Data
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The CJ1W-PRT21 forms a link between two bus systems: the host PLC's I/O
bus on one side, and PROFIBUS-DP on the other. The Unit can be consid-
ered as a slave to both systems: the I/O bus communication is controlled by
the CPU Unit of the host PLC, the PROFIBUS-DP communication is control-
led by a PROFIBUS-DP master.
Being a slave of two systems may cause confusion as to which data should
be considered 'input data' and which is 'output data'. In this manual all I/O
data communication is defined from the point of view of the PROFIBUS-DP
system:
Slave INPUT Data is process data which the CJ1W-PRT21 reads from the
assigned areas on demand of the host PLC. The CJ1W-PRT21 sends this
data to the PROFIBUS-DP master unit.
Host PLC
I/O Bus
Figure 1 Slave INPUT data direction
Slave OUTPUT Data is process data which the CJ1W-PRT21 receives from
the PROFIBUS-DP master unit. The CJ1W-PRT21 writes this data to the
assigned areas on demand of the host PLC.
Host PLC
I/O Bus
Figure 2 Slave OUTPUT data direction
CJ1W-PRT21
PROFIBUS
CJ1W-PRT21
PROFIBUS
Section 4-1
PROFIBUS
Master
PROFIBUS
Master