Modbus function reference
Modbus Function Code 02 — Read Discrete Inputs
Read packed read-only boolean states
02
Read packed read-only boolean states
Data model
Discrete inputs (1xxxx reference family)
Access
Read packed read-only boolean states
Protocol quantity
1–2000 discrete inputs
Worked example
Read 22 discrete inputs beginning at protocol address 196. Unused bits in the final response byte are padding.
Typical use: Polling read-only field or status bits such as limit switches, trip feedback and device-ready states.
Request PDU
02 00 C4 00 16Normal response PDU
02 03 AC DB 35PDU 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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