5-27
5 Operation
CJ-series PROFIBUS Master Unit Operation Manual for NJ-series CPU Unit (W509)
5-5 I/O Communication Characteristics
5
5-5-2 Mapping I/O Data
Auto Addressing
The default allocation of I/O modules, i.e. I/O modules are mapped in ascending order of slave
addresses and module selection, uses the concept of Auto Addressing of the CJ1W-PRM21 Master
DTM. Auto Addressing will (re)allocate I/O modules according to the algorithm explained above in
each area.
If a configuration has been selected, which is changed later by adding an I/O module to one of the
slaves, the Auto Addressing feature will add that module to the default area between the already
selected modules of that particular slave device.
Precautions for Correct UsePrecautions for Correct Use
When an I/O module is added to or deleted from a configuration at a later point in time, Auto
Addressing will cause a change in the addresses of subsequent I/O modules in an Input/Output
area. This will cause I/O data of (a part of the) slave devices to be re-mapped to different loca-
tions in the CPU memory. In order to avoid unexpected results, the CPU user program and User
Defined Variables may have to be adapted as well.
Note 1 Auto Addressing will not change the allocation of I/O modules to a certain area, i.e. a mod-
ule allocated to Input/Output area 2 will not be re-allocated to area 1 if Auto Addressing is
enabled.
2 Auto Addressing will not change the start address of the areas.
3 Auto Addressing is by default enabled, when starting a new project. It is however, disabled
for existing projects to avoid unwanted re-mapping.
The figure below shows an example of the effects of Auto Addressing on (re)allocation of I/O mod-
ules. In the original I/O configuration on the left, the first slave - an OMRON CJ1W-PRT21 - con-
sisted of two I/O modules. In new configuration one I/O module was inserted, and subsequent
modules were re-allocated in the process.
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