Use Of The Modbus Functions - WAGO 750 Series Manual

6.2 Use of the MODBUS Functions

The example below uses a graphical view of a fieldbus controller to show
which MODBUS functions can be used to access data of the process image.
FC 3 (
1 1
3
Fig. 6-1: Use of the MODBUS Functions
Attention
It is recommended that analog data be accessed with register functions and
digital data with coil functions .
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
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Ethernet
ON
LINK
TxD/RxD
ERROR
I/O
Input modules 750- 402 402 472 472 402 476 402 476
Read Multiple Registers )
FC 4 (Read Input Registers)
MODBUS addresses
0x0000 Word1 Word2
0x0001 Word2 Word2
Word2 Word1
0x0002
Word2 Word2
0x0003
0x0004 Word2 Word1
0x0005 Word2 Word2
0x0006 Word2 Word1
0x0007
Word2 Word2
0x0008
Highbyte Lowbyte
FC 1 ( Read Coils)
FC 2 ( Read Input Discretes
MODBUS
addresses
0x0000
0x0001
0x0002
0x0003
0x0004
2
0x0005
0x0006
0x0007
0x0008
0x0009
0x000A
0x000B
0x000C
0x000D
0x000E
0x000F
Use of the MODBUS Functions
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AI
FC 16 (
FC 3 (
)
MODBUS Functions
Output modules 750- 501 550 550
FC 6 (Write Single Register )
Write Multiple Registers)
MODBUS addresses
0x0000 / 0x0200 Word2 Word1
0x0001 / 0x0201 Word2 Word2
1
0x0002 / 0x0202
Word1 Word2
0x0003 / 0x0203
Word2 Word2
0x0004 /
3
0x0204
Highbyte Lowbyte
Read Multiple Registers)
FC 4 ( Read Input Registers)
MODBUS addresses
Word1 Word2
0x0200
Word2 Word2
0x0201
1
0x0202
Word2 Word1
0x0203
Word2 Word2
3
0x0204
Highbyte
Lowbyte
FC 5 (Write Coil)
FC 15 (Force Multiple Coils)
MODBUS addresses
0x0000 / 0x0200
2
0x0001 / 0x0201
FC 1 ( Read Coils)
FC 2 ( Read Input Discretes)
MODBUS addresses
0x0200
2
0x0201
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DO
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