6 Application example: Modbus TCP
6.3 Communication examples: Modbus TCP
XI/ON: XNE-GWBR-2ETH-MB
10/2011 MN05002008Z-EN
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Digital modules
The process image length of the digital modules is also read via function code 04. The data
are stored in register 0×1013:
The process image length of all digital input modules of the example station is:
0×0A bits = 10 bits
6.3.5
Reading-out the packet process data (inputs)
In order to assure a largely efficient access to the process data of a station, the module data
are consistently packed and mapped to a coherent register area.
The packed input data can be found in registers 0×0000 to 0×01FF of the gateway. They can
be accessed via function code 03..
The first 9 registers (18 bytes) contain the input data of the intelligent modules "
A
", followed
by 1 register of digital input data "
B
".
Figure 55:
Process data
length of digital
input modules
Table 64:
Process input
data of digital
modules
Module
Process input
1
XN-2DI-24VDC-P
2 bits
4
XN-4DI-24VDC-P
4 bits
8
XN-4DI-24VDC-P
4 bits
Total
10 bits
Figure 56:
Packed input
process data
A
B
