Simply Modbus logo Modbus tester for serial communication diagnostics





RTU Master

RTU Slave

TCP Client






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Data Communication Test Software


Simply Modbus Master

Modbus RTU Master and Modbus ASCII Master Software

RTU Master screenshot


 Functions as a Modbus RTU Master or Modbus ASCII Master

 Connects to RTU or ASCII Slave devices using the Modbus protocol

All information to send and receive messages is displayed in one window.


       Supported Register Function codes:

Function Code Action Table Name
04 (04 hex) Read Analog Input Registers
03 (03 hex) Read Analog Output Holding Registers
06 (06 hex) Write single Analog Output Holding Register
16 (10 hex) Write multiple Analog Output Holding Registers

       Supported Coil Function codes:

Function Code Action Table Name
02 (02 hex) Read Discrete Input Contacts
01 (01 hex) Read Discrete Output Coils
05 (05 hex) Write single Discrete Output Coil
15 (0F hex) Write multiple Discrete Output Coils


Change the reply data types and byte and word ordering with a click
to determine the format of a reply string without having to send another message.

Supports multiple data types in the same message.

 Supports Standard Modbus and Enron Modbus

Can use RTS delay (required for some radios)


Supports 2 byte slave IDs

A notes column allows labeling the results

Allows saving and restoring settings in Configuration Files.

Write window allows writing single and multiple values

Save the Byte History Log to a text file

Log Data to a tabbed text file

and more...

See the online manual

See the tutorial to Learn about Modbus and How it Works


Free Download

All unlicensed programs

run in demo mode

with full functionality.

Demo mode allows sending and receiving six messages.

The programs can always be restarted to reset the demo
and send and receive more messages.


Compiler 14
118 MB - click to download



Compiler 7

Quick Install Program. puts a shortcut in the start menu.
8.60 MB - click to download



Compiler 5 - For windows XP

No Install Program. Just download, unzip and double click the exe file.
1.70 MB - click to download


Known Issue:  Some users experience version 6.4.1 quitting by itself
or requiring an 'end task' to close properly.



Download the demo and try before you buy.

Quantity Simply Modbus
1 license
for 1 user or 1 PC
2 licenses
for 2 users or 2 PCs
site license
unlimited installations
at one location
within a single company

Prices in US dollars.


Combine purchase with other programs for savings.


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