Click to Shopping Cart    |    Sitemap    |    Contact Us    
     
 

Modbus RTU Function 03 - Read Holding Registers

The Modbus RTU Function 03 is used to Read Holding Registers, (4x register references), in a Modbus Slave device. Registers are addressed starting at zero: meaning registers 110 are addressed as 09.

Modbus Function 03 also includes the quantity of registers to read from the Modbus slave device.  See the example command below that reads one register, 40010 from Modbus Slave address 01.

  D6400 Thermocouple, 4-20mA Input Module
Measure Seven Thermocouple or 4-20mA Current Loops!
Using the Modbus RTU Protocol
 
Command: 01 03 00 09 00 01 CRC1 CRC2
Response: 01 03 02 7C 93 CRC1 CRC2  

Command Usage:

Address01 - One Byte Slave Address
Function03 - One Byte Function Number
Addr00 - Starting Register Address HI Byte
Addr09 - Starting Register Address LO Byte
Data00 - HI Number of Registers
Data01 - LO Number of Registers
ChecksumTwo Byte CRC

Response Message:

Address01 - One Byte Slave Address
Function03 - One Byte Function Number
Byte Qty02 - Number of data bytes in response
Data HI7C - Data Register HI Byte
Data LO93 - Data Register LO Byte
ChecksumTwo Byte CRC
  
Finally, when specifying Modbus hardware or software, take a moment to review the documentation for each item and ensure that both the hardware and software will support the necessary functions to operate properly. It is a rare event that there will be problems but this review process will eliminate the possibility of surprises later.

Return to Modbus Overview
Modbus Exception/Error Codes

Modbus Data Acquisition Products:
Modbus RTU Products
Click Here
 
 
 
Modbus Products
ASCII Products
Accessories
Support
Purchase
Company  
  D1000M Series
  D1700M Series
  D3000M Series
  D5000M Series
  DIN-100 Series
  D6000 Series
  D8000 Series
  D1000 Series
  D1700 Series
  D2000 Series
  D3000 Series
  D4000 Series
  D5000 Series
  Mounting Backplanes
  Module Accessories
  Serial Converters
  USB Converter
  Power Supplies
  Software
  Cables
  FAQ's
  Data Sheets
  Diagrams
  User Manuals
  Product Finder
  Modbus Support
  Contact Support
  Product Warranty
  How to Buy
  Shop Online
  International
  View Shopping Cart
  About Us
  Contact Us
  Policies
  Sitemap
  Blog
  Join our Email List

        
 
 
Copyright Dutile, Glines & Higgins Corporation,
All Rights Reserved.