Walchem W600 - Function Code 1, Read Coils; Function Code 2, Read Discrete Inputs

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4.1.3.1 Function Code 1, Read Coils
Read Coils Request PDU
Name
Size
Description
Function Code
1 Byte
Function Code Identifier (0x01).
Starting Address
2 Bytes
The data address of the first Coil to read.
Quantity of Coils
2 Bytes
The number of Coils requested, maximum of 2000 per message.
Read Coils Response PDU
Name
Size
Description
Function Code
1 Byte
Function Code Identifier (0x01).
Byte Count
1 Byte
The number of data bytes to follow.
Coil Status
1-125 Bytes
8 Coils per byte, up to 2000 Coils per message.
Read Coils Exception PDU
Name
Size
Description
Error Code
1 Byte
0x80 plus Function Code Identifier (0x81).
Exception Code
1 Byte
See 4.1.4 Modbus/TCP Exception Error Codes
4.1.3.2 Function Code 2, Read Discrete Inputs
Read Discrete Inputs Request PDU
Name
Size
Description
Function Code
1 Byte
Function Code Identifier (0x02).
Starting Address
2 Bytes
The data address of the first Discrete Input to read.
Quantity of
Discrete Inputs
2 Bytes
The number of Discrete Inputs requested, maximum of 2000 per
message.
Read Discrete Inputs Response PDU
Name
Size
Description
Function Code
1 Byte
Function Code Identifier (0x02).
Byte Count
1 Byte
The number of data bytes to follow.
Discrete Input
Status
1-125 Bytes
8 Discrete Inputs per byte, up to 2000 Discrete Inputs per
message.
Read Discrete Inputs Exception PDU
Name
Size
Description
Error Code
1 Byte
0x80 plus Function Code Identifier (0x82).
Exception Code
1 Byte
See 4.1.4 Modbus/TCP Exception Error Codes