Walchem W600 - Function Code 3, Read Holding Registers; Function Code 4, Read Input Registers

9
4.1.3.3 Function Code 3, Read Holding Registers
Read Holding Registers Request PDU
Name
Size
Description
Function Code
1 Byte
Function Code Identifier (0x03).
Starting Address
2 Bytes
The data address of the first Holding Register to read.
Quantity of
Holding Registers
2 Bytes
The total number of Holding Registers requested, maximum of
125 per message.
Read Holding Registers Response PDU
Name
Size
Description
Function Code
1 Byte
Function Code Identifier (0x03).
Byte Count
1 Byte
The number of data bytes to follow.
Holding Register
Values
2-250 Bytes
1 Holding Register for every 2 bytes, maximum of 125 Holding
Registers per message.
Read Holding Registers Exception PDU
Name
Size
Description
Error Code
1 Byte
0x80 plus Function Code Identifier (0x83).
Exception Code
1 Byte
See 4.1.4 Modbus/TCP Exception Error Codes
4.1.3.4 Function Code 4, Read Input Registers
Read Input Registers Request PDU
Name
Size
Description
Function Code
1 Byte
Function Code Identifier (0x04).
Starting Address
2 Bytes
The data address of the first Input Register to read.
Quantity of Input
Registers
2 Bytes
The total number of Input Registers requested, maximum of 125
per message.
Read Input Registers Response PDU
Name
Size
Description
Function Code
1 Byte
Function Code Identifier (0x04).
Byte Count
1 Byte
The number of data bytes to follow.
Input Register
Values
2-250 Bytes
1 Input Register for every 2 bytes, maximum of 125 Input
Registers per message.
Read Input Registers Exception PDU
Name
Size
Description
Error Code
1 Byte
0x80 plus Function Code Identifier (0x84).
Exception Code
1 Byte
See 4.1.4 Modbus/TCP Exception Error Codes