A tool for response time and schedulability analysis in modbus serial communications

The use of Modbus protocol for industrial control and monitoring applications over multipoint RS-485 networks may be constrained by several factors, as the number of messages exchanged over the network and their respective bandwidth usage. Some applications need an evaluation of the response times of a set of messages to ensure that the set is schedulable, according to the application requirements, as message periods, deadlines and scheduling policy. In this paper, we discuss a tool for response time and schedulability analysis for Modbus communications over RS-485 networks. Response times of a message set are collected by a specialized Modbus device and then sent to software where analysis is done. A Modbus application over a RS-485 network was deployed in a laboratory environment for evaluation using the developed tool.