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94
I/O Communication Characteristics
Section 3-5
The example shows that the sequence of slave addresses is maintained, the
sequence of I/O modules selected is maintained and the I/O modules are allo-
cated to the lowest address of the area.
Enable/Disable Auto
Addressing
The Auto Addressing feature can be disabled in the CS1/CJ1W-PRM21 Mas-
ter DTM. In order to do that, perform the following sequence.
1,2,3...
1.
Open the CS1/CJ1W-PRM21 Master DTM - Configuration User Interface.
2.
Select the Master Setup tab.
3.
Enable/Disable Auto Addressing by selecting/deselecting the Auto Ad-
dressing checkbox in the Support box.
4.
When Auto Addressing is being enabled, a warning message is displayed,
informing the user of the effects of enabling Auto Addressing.
!Caution
Enabling Auto Addressing has the immediate effect of re-allocating I/O mod-
ules of an existing configuration, within each Input/Output area. The I/O mod-
ules are re-mapped according to the algorithm described above.
Note
Disabling Auto Addressing has no immediate effect on an existing I/O map-
ping.
I/O Mapping Without Auto
Addressing
A disabled Auto Addressing feature has the following effects on I/O mapping:
• When adding new slave devices or new I/O modules to an existing slave
configuration, the I/O modules will be mapped to the first I/O areas, but
the modules will be appended to the existing I/O mapping.
• When deleting a slave device from the network configuration, or deleting
I/O modules from a slave device, the deleted I/O modules will leave gaps
behind in the already existing I/O mapping. If after deleting an I/O module
a slave device still has more than one module configured, but these mod-
ules are not in the same place, the DTM will attempt to remap them
together.
• Changing the address of a slave device, of which already an I/O mapping
exists, has no effect on the existing mapping
• Selecting an additional I/O module for a slave device, in the presence of
already allocated I/O modules, will cause a complete re-map of all exist-
ing modules if the total I/O does not fit within the space it is already occu-
pying. The modules are re-mapped to the next available location in the
area, leaving behind a gap in the existing I/O mapping. Subsequent I/O
modules of other slave device will remain mapped as before the module
addition.
• When moving an I/O module from one area to another, they can be
located anywhere with in the target area. They are not re-mapped to the
start of that.
• When moving an I/O module from one area to another, the module leaves
behind a gap in the I/O mapping of the first area.
Note
1.
Gaps in the I/O mapping still contribute to the total size of an area, although
they do not contain valuable data. They therefore decrease the total I/O ca-
pacity of the CS1/CJ1W-PRM21 PROFIBUS Master Unit, and unneces-
sarily occupy PLC memory.
2.
In the I/O data exchange with the PLC CPU, these gaps will contain zeros.