ise smart connect Modbus Vaillant
Modbus TCP/IP
Order No.
S-0002-007
Product Manual Page 16 (45)
4
Modbus TCP/IP
4.1
Modbus function codes
The following function codes are supported via Modbus TCP/IP:
Function
code
Hex
Name
03
0x03
Read Holding Registers
04
0x04
Read Input Registers
06
0x06
Write Single Register
16
0x10
Write Multiple Registers
4.2
Modbus exception codes
The following exception codes can be generated by the gateway:
Exception
code
Hex
Name
Description
01
0x01
Illegal Function Code The function code is unknown to the server
02
0x02
Illegal Data Address
Data Address not accessible (dependant on the request)
03
0x03
Illegal Data Value
Data Value not supported (dependant on the request)
04
0x04
Server Failure
The server failed during the execution
11
0x0B
Gateway Target
Device Failed To
Respond
Indicates that no response was obtained from the target
device (unit ID).
Usually means that the device (unit ID) is not present on
the network.
4.3
Modbus TCP/IP Gateway behaviour
All addresses are one-based. If you request register 1, you get the value of register 1.
For 32-bit data points, the first register contains the least significant word.
32-bit data points (two registers) can only be written contiguously with function code 0x10 (Write
Multiple Registers). Write requests, which try to set only 16-bit (one register) of a 32-bit data
point (two registers) are responded with exception code 0x02 (Illegal Data Address).
Requests to non-existing/inactive unit IDs are responded with exception code 0x0B (Gateway
Target Device Failed To Respond).
