The following table lists the specific Modbus function codes used for communicating by all of the Modbus drivers included in the TOP Server Modbus Suite:ĭepending on which type of address (holding register, internal register, input coil or output coil) you are reading or writing from your client application, that will determine which specific function code the TOP Server Modbus driver will use in the actual protocol request to your device. holding registers, input coils, etc) to access and what action to perform on that memory (i.e. Modbus Function Codes Supported by TOP ServerĪ function code (FC) in Modbus is a specific code used in a Modbus request to tell the Modbus slave device what type of memory (i.e. So, in this post, I'm going to discuss the Modbus functions codes that TOP Server uses to read and write the different types of Modbus memory addresses and how they correspond to the actual addresses your client is requesting, using TOP Server for Wonderware applications as an example. I know some of you who read that post were looking for a little more depth on how specific Modbus function codes come into play. In my previous blog post Demystifying Modbus Register Addressing, I discussed how confusing Modbus addressing can be due to how different device manufacturers describe their implementations in their device manuals. In this blog post, I will step through the specifics of Modbus function codes and how they pertain to addressing, and how they affect what addresses to use in TOP Server for Wonderware applications. Sometimes a device manual might only refer to the supported Modbus function codes and the range of offsets available for those function codes. With the wide range of devices that use Modbus for their communication protocol, you'll find many different interpretations, terminology and labels with respect to how to access different types of data in those devices.

Pm 5340 modbus rtu over tp