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HomeResourcesModbus GlossaryFC06 — Write Single Register
Function CodesModbus Term

FC06 — Write Single Register

Write a 16-bit value to a single holding register.

Definition

Function Code 06 writes a single 16-bit value to one holding register. The slave echoes back the request on success. It is simpler than FC16 (Write Multiple Registers) when only one register needs updating. Values are unsigned 16-bit (0–65535), but most devices interpret them as signed or as part of a multi-register data type.

Quick Facts

FC hex0x06
Write count1 register only
ResponseEcho of request
Use FC16 forMultiple registers or 32-bit values

Example

Request (write 0x00C8 = 200 to register address 1, slave 1):
01 06 00 01 00 C8 98 4A

Response (echo of request):
01 06 00 01 00 C8 98 4A

Related Terms

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ModPackQT Modbus Glossary · Updated 2026