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Function CodesModbus Term

FC02 — Read Discrete Inputs

Read the ON/OFF state of one or more digital inputs (read-only coils).

Definition

Function Code 02 reads the state of discrete input bits (1x register range). These are read-only digital signals — typically physical inputs from sensors, push-buttons, or limit switches. Like FC01, the response packs bit values LSB-first. Up to 2000 inputs can be read in one request.

Quick Facts

FC hex0x02
Register typeDiscrete Inputs (1x / 10001–19999)
AccessRead-only
Max per request2000 inputs

Related Terms

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ModPackQT Modbus Glossary · Updated 2026