34
•
Fieldbus coupler 750-342
Data exchange
Modular I/O System
ETHERNET TCP/IP
3.1.5.3
Data exchange between MODBUS master and I/O modules
The data exchange between the MODBUS master and the I/O modules is ma-
de 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:
•
Input words
•
Output words
•
Input bits
•
Output bits
The word for word access to the digital input and output modules is made in
accordance with the following table:
Digital inputs/
outputs
16.
15.
14.
13.
12.
11.
10.
9.
8.
7.
6.
5.
4.
3.
2.
1.
Process data
word
Bit
15
Bit
14
Bit
13
Bit
12
Bit
11
Bit
10
Bit
9
Bit
8
Bit
7
Bit
6
Bit
5
Bit
4
Bit
3
Bit
2
Bit
1
Bit
0
Table 3.3: 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.
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.
0x000
0x0FF
0x000
(0x200)
0x0FF
(0x2FF)
PII = Process Input
Image
PIO = Process Output
Image
MODBUS master
PII
PIO
I/O modules
Inputs
Outputs
Fieldbus Coupler
Fig. 3-10: Data exchange between the MODBUS master and I/O modules
g012927e
Содержание I/O-SYSTEM 750
Страница 334: ...330 Notes Modular I O System ETHERNET TCP IP ...