Industrial protocols

Modbus register address translator

Translate between zero-based PDU offsets, one-based register numbers and Modicon-style references.

Calculate

Source address
Coils and holding registers are read/write; discrete inputs and input registers are read-only.
Use the convention shown in the device manual. PDU offsets begin at 0; table numbers begin at 1; labelled references include the object-table prefix.

Worked example

Zero-based PDU offset

0 

PDU offset in hexadecimal
0x0000
One-based number within table
1
Classic labelled reference
40001
Six-digit labelled reference
400001

Holding register. Confirm whether the device manual expects a zero- or one-based entry before configuration.

Method and assumptions

Formula

PDU offset = one-based number − 1; labelled references add an object-table base

The protocol transmits a zero-based offset. 0xxxx/1xxxx/3xxxx/4xxxx and six-digit references are documentation conventions, not PDU addresses.

Limits of this result

  • Confirm the source data, device datasheet and installation conditions before relying on the result.

Technical sources

  1. MODBUS Application Protocol Specification V1.1b3Modbus Organization · 2012-04-26
  2. An Introduction to ModbusModbus Organization · accessed 2026-09-14

Put the value to work

Read the related engineering guidance, or carry this task into System Builder to identify the signal path and EpiSensor products.

Continue in System Builder Read: What Is SCADA?

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