WAGO 750 Series Manual page 57

3.1.5.3 Data exchange between MODBUS/TCP master and I/O modules
The data exchange between the MODBUS/TCP master and the I/O modules is
made by the implemented MODBUS functions in the coupler with reading and
writing in bits or bytes.
The controller handles four different types of process data:
•
•
•
•
The word for word access to the digital input and output modules is made in
accordance with the following table:
Digital Inputs/Outputs
Process data word
Byte
Table 3.1.2: Allocation of digital inputs/outputs to process data word acc. Intel format
The outputs can be read back by adding 0x0200 to the MODBUS address.
Fig. 3.1-10: Data exchange between the MODBUS master and I/O modules
Starting from address 0x1000 there are the register functions. The register
functions made available in the coupler, can be addressed by the MODBUS
master along with the implemented MODBUS function codes (read/write). To
this effect, the individual register address is entered in place of the address of
a module channel.
More information
You can find a detailed description of the MODBUS addressing in the
chapter „MODBUS Register Mapping".
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
Input words
Output words
Input bits
Output bits
16.
Bit
15
High-Byte
D1
MODBUS master
0x000
PII
0x0FF
Inputs
I/O modules
Fieldbus Coupler
15. 14. 13. 12. 11. 10. 9.
Bit Bit Bit Bit Bit Bit
14 13 12 11 10 9
0x000
(0x200)
PIO
0x0FF
(0x2FF)
Outputs
Fieldbus coupler 750-342 • 51
Data exchange
8. 7. 6. 5. 4.
Bit Bit Bit Bit Bit Bit
8 7 6 5 4 3
Low-Byte
D0
PII = Process Input
Image
PIO = Process Output
Image
3. 2. 1.
Bit Bit Bit
2 1 0
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