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Endianness & Byte-Swapping

Written by Benjamin Pinnerup

Updated at December 6th, 2024

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Table of Contents

Introduction Endianness Byte-Swapping

Articles in this section:

  • Modbus TCP - Instance & item setup
  • Word (endianness) & Byte-Swapping
  • Modbus RTU - Instance & Item setup

 

Introduction

Across various brand and utilization of the Modbus protocol, endianness and byte-swapping has been introduced. To better support the variations across Modbus, SIA Connect allows you to configure the reading of Modbus registers. A register has the size of a single word, 2 bytes. 

Endianness

Endianness is applied when reading values that span across more than one register - eg. INT32, FLOAT, DWORD, etc. 

You can choose between big endian and little endian. 

Big endian Little endian
  1. Register 1
  2. Register 2
  1. Register 2
  2. Register 1

 

Byte-Swapping

Byte-swapping is applied for each individual register being read. You can choose between First Byte High and First Byte Low

First byte high First byte low
  1. Byte 1
  2. Byte 2
  1. Byte 2
  2. Byte 1

 

word sequence byte order byte swapping endianness word swapping

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Related Articles

  • Modbus TCP - Instance & item setup
  • Modbus RTU - Instance & Item setup

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