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HomeResourcesModbus GlossaryFC15 — Write Multiple Coils
Function CodesModbus Term

FC15 — Write Multiple Coils

Write ON/OFF states to a block of coils in a single request.

Definition

Function Code 15 forces multiple coils to specified states. Coil values are packed into data bytes with the first coil in the LSB of the first byte. The response returns the slave address, function code, starting address, and quantity written — not the full data. Up to 1968 coils can be written in one request.

Quick Facts

FC hex0x0F
Max coils1968 per request
Bit packingLSB of first byte = first coil

Related Terms

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ModPackQT Modbus Glossary · Updated 2026