Conformance test Modbus/ASCII


Thread Starter

Gary Lynch

Three years ago I wanted to conformance test a Modbus slave that supported the Modbus/TCP protocol. After consulting with this forum, I purchased the Modbus TCP Conformance Testing Program, and was able to complete testing of the device on schedule with no additional hassle.

This year I am facing the same task, but for a Modbus slave that supports Modbus/ASCII. A quick review of the Conformance Testing Program gives the impression that it only supports the TCP protocol and there is no other testing program available.

How do I test my device?

Lenore Tracey

The Modbus Organization's Conformance test program does include testing of devices that communicate using Modbus over serial line.

According to the test spec: "The Protocol Test, acting as a Modbus Client, assesses Modbus conformance by checking the server’s supported Modbus Function codes. Additionally it will test for message error handling and message format error handling. If the Server passes each required Criterion, it is declared a Conformant Server for the current test revision. The test setup is based on using Modbus TCP. For Modbus TCP devices, the connection is made over TCP/IP. For Modbus Serial devices, a properly configured Schneider Electric ETG-100 Modbus Ethernet-to-Serial Gateway is used."

For pretesting other Modbus Ethernet-to-Serial Gateways can also be used.

You can download the test spec from the website ( Email [email protected] for more information.

Hope this is helpful.

(Modbus Organization, Inc.)