750-841 WAGO, 750-841 Datasheet - Page 163

• Manufacturer Part Number: 750-841
• Description: CONTR.ETHERNET TCP/IP 10/100MBIT
• Manufacturer: WAGO

Specifications of 750-841

• Rohs Compliant: YES
• No. Of Digital Inputs: 10
• No. Of Digital Outputs: 10

4.2.3.3 Function Code FC3 (Read multiple registers)
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
This function reads the contents of holding registers from a slave device in
word format.
Request
The request specifies the reference number (start register) and the word count
(register quantity) of the registers to be read. The reference number of the
request is zero based, therefore, the first register starts at address 0.
Example: Read registers 0 and 1:
Response
The reply register data is packed as 2 bytes per register. The first byte contains
the higher value bits, the second the lower values.
The contents of register 0 are displayed by the value 0x1234 and the contents
of register 1 is 0x2345.
Exception
Byte
Byte 0, 1
Byte 2, 3
Byte 4, 5
Byte 6
Byte 7
Byte 8, 9
Byte 10, 11 Word count
Byte
.....
Byte 7
Byte 8
Byte 9, 10
Byte 11, 12 Value Register 1
Byte
.....
Byte 7
Byte 8
Value Register 0
Field name
Transaction identifier
protocol identifier
length field
unit identifier
MODBUS function code
reference number
Field name
MODBUS function code
Byte count
Field name
MODBUS function code
Exception code
Example
0x0000
0x0000
0x0006
0x01 not used
0x03
0x0000
0x0002
Example
0x03
0x04
0x1234
0x2345
Example
0x83
0x01 or 0x02
Fieldbus Communication
MODBUS Functions
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