Reducing update data time for exchange via MODBUS TCP protocol by controlling a frame length

Abstract

Despite the fact that the MODBUS protocol has been widely used in industrial automation systems, its capabilities are limited by the published standard. In this article improvement of the exchange between the industrial equipment and HMI-system, supporting the MODBUS implementation for Ethernet networks, are discussed. The experimentally measured values of the average request-response cycle time, jitter and time intervals consumed by each of the exchange participants are presented. The method of reducing the update data time using the procedure for grouping the required slave memory cells into requested via MODBUS blocks of optimal length has been proposed. The experimental results of this MODBUS protocol improvement and some comparisons have been presented and discussed.