MODBUS APPLICATION AT JEFFERSON LAB

Abstract

Modbus is a client/server communication model. In our applications, the embedded Ethernet device XPort is designed as the server and a SoftIOC running EPICS Modbus is the client. The SoftIOC builds a Modbus request from parameter contained in a demand that is sent by the EPICS application to the Modbus Client interface. On reception of the Modbus request, the Modbus server activates a local action to read, write, or achieve some other action. So, the main Modbus server functions are to wait for a Modbus request on 502 TCP port, treat this request, and then build a Modbus response.