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Data ModelModbus Term

Input Register (3x Registers)

A 16-bit read-only register — typically live sensor or process values.

Definition

Input registers are 16-bit read-only registers that hold values the slave produces — ADC readings, temperature, pressure, flow, voltage, etc. They occupy the 3x address range (30001–39999 in 1-based). A master can only read them, not write. Some devices map identical data to both 3x (input) and 4x (holding) ranges.

Quick Facts

Word size16-bit unsigned
0-based range0–65535 (in 3x table)
1-based range30001–39999
Read withFC04
WriteNot possible from master

Related Terms

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ModPackQT Modbus Glossary · Updated 2026