DL-1xxS-WF Series User’s Manual
DL-1xxS-WF Series
User’s Manual (Rev1.0,May/2022) ------------- 22
4.
Modbus Protocol
4.1.2
Function Code
The function code field of a Modbus data unit is coded in one byte. Valid codes are
in the range of 1 ... 255 decimal (the range 128 - 255 is reserved and used or exception
responses). When a Modbus request is sent from a Modbus Client to a Server device the
function code field tells the Server what kind of action to perform.
The Modbus TCP feature of DL-1xxS-WF supports 5 function codes, which allows
the reading and writing of data contents of registers.
Function Code
Descriptions
01 (0x01)
Read multiple Coil Status
03 (0x03)
Read multiple Analog Output registers
04 (0x04)
Read multiple Analog Input registers
05 (0x05)
Force Single Coil
06 (0x06)
Write single Analog Output registers register
Table 4-1: Supports Function Codes of DL-1xxS-WF
Any other function code request will be returned with an error response indicating
the function code is not supported, as well as a request for too much data or data at a
register address that not present.
4.1.3
Error Response
Byte Index
Field Name
Byte count
Description
00
Address
1 Byte
1 to 247
01
Function code
1 Byte
Function code + 0x80
02
Exception code
1 Byte
01
Table 4-2: Error response of Modbus Protocol
If a CRC mismatch occurs, the module will not respond.
