Modbus function reference
Modbus Function Code 05 — Write Single Coil
Write one boolean output state
05
Write one boolean output state
Data model
Coils (0xxxx reference family)
Access
Write one boolean output state
Protocol quantity
Exactly 1 coil
Worked example
Write ON to the coil at protocol address 172. ON is encoded FF00 and OFF is encoded 0000.
Typical use: Sending a single boolean command when the device map explicitly permits a coil write.
Request PDU
05 00 AC FF 00Normal response PDU
05 00 AC FF 00PDU examples omit the Modbus TCP MBAP header and the Modbus RTU unit-address/CRC envelope. Multi-byte values are shown in network byte order.
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