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Data ModelModbus Term

Holding Register (4x Registers)

A 16-bit read/write register — the most used data store in Modbus.

Definition

Holding registers are 16-bit read/write memory locations. They store setpoints, configuration values, counters, and process data. Most Modbus devices expose the bulk of their functionality through holding registers. They occupy the 4x address range (40001–49999 in 1-based notation). Each register stores one 16-bit unsigned word, but devices often combine adjacent registers for 32-bit values.

Quick Facts

Word size16-bit unsigned
0-based range0–65535
1-based range40001–49999
Read withFC03
Write withFC06 (single), FC16 (multiple)

Related Terms

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ModPackQT Modbus Glossary · Updated 2026