The new coil value is the value written to the coil.
Table 6-9 Write coil normal response messages
Message byte Example
Slave address xxhex
Function code 05hex
Coil address Upper xxhex
Lower xxhex
New coil value Upper FFhex or 00hex
Lower 00hex
CRC-16 Lower xxhex
Upper xxhex
Exception response
The exception response message contains the same slave address as the command message.
The function code of the exception message is actually a value of 80 hex plus the original
function code of 05hex . The exception code indicates where the error occurred in the command
message. A complete listing of exception codes is shown in a later chapter
Table 6-10 Write coil exception response messages
Message byte Example
Slave address xxhex
Function code 85hex
Exception code 01hex to 06hex
CRC-16 Lower xxhex
Upper xxhex
Examples
Coil 0 (Restart Modbus communication)
To activate a new baudrate and parity/framing the coil 0 (restart Modbus communication) must
be send. Otherwise a power down/up initiate a new baudrate and parity/framing:
• Query: 1,5,0,0,255,0,140,58 (Hex 01,05,00,00,FF,00,8C,3A) (Set coil 0 to 0xFF00)
• Receive: 1,5,0,0,255,0,140,58 (Hex 01,05,00,00,FF,00,8C,3A) (Restart Modbus
communication)
Functions codes
6.4 Write single coil
Modbus RTU RS 485
Operating Instructions, 03/2021, A5E00753974-AB 29
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