I have an application using Control Logix and a purchased device using Modbus Ethernet TCP/IP. so far I cannot find any supplier that can support the Modbus Function Code 43 which I need to use to tranfer data between Control Logix PLC and the device needing the data. So far Molex, Anybus, Red Lion, Prosoft & Kepserver do not support this code. Has anyone run ito this and solve the communications?

 

This is not a standard Modbus fucntion code. It is a custom code that is specific to the manufacturer of the hardware. All modbus capable devices should support the ability to read and write to Input and output coils, input registers and holding registers to say that they are modbus compliant. In the protocol it is acceptable to use special customer specific function codes. Since these codes are specific to the hardware manufacturer it is up to that manufacturer to provide a way to get the data accessed but these special function codes out of the device.

Typically the manufacturers will do this with activeX controlls that can be loaded into Excel or some other windows based application. The problem with that is that you cannot easily get that data into your historians or make it avaialbel to other hardware.

With Kepserver you can use the UCON (user configurable driver) to create a customer driver that can access this data. We have done so for several customers and have others that have done it for them selves.

Fred Loveless
Senior Application Engineer
Kepware Technologies
http://www.kepware.com

 

Function code 43 is the "Encapsulated Interface Transport". It is used to tunnel non-Modbus data and requests inside a Modbus message. There are different type codes for different types of tunneling.

You are more than a little vague about what sort of "support" you are looking for. It is not really possible to provide an answer based on the information you have given. You have just told us that "something" doesn't support Function 43, but you haven't said what this "something" needs to do or where it would fit into your network or what relationship it would have to your AB PLC or the "purchased device".

 

We have a lot of experience talking with "Modbus" devices and we only have seen only one, a Danload 6000 that uses Function Code 43. It, in fact, uses both function codes 42 and 43. We have a driver for this protocol that will convert it to standard Modbus. If this is what you need, please contact me at jmiille (at) miille.com.

The previous posters are correct, anyone can use "special function codes" as long as they define what they do.

We also offer an Ethernet port that is compatible with Ethernet/IP and Modbus/TCP if that is were you need to go.

Thanks,
Jerry Miille