Abstract:

Modbus/TCP industrial Ethernet standard cannot guarantee the realtime capability by itself. A token ring scheduling algorithm is designed, which uses priority to achieve the realtime response to highpriority Modbus/TCP messages. Based on that, a weighted token ring scheduling algorithm and a weightvariable token ring scheduling algorithm are developed to meet the customizable and changeable time delay demands. Finally, the response delay on a μC/OSII+ARM7 platform is measured to be 1.15±0.15ms, which is superior to most current researches that aim at improving the realtime capability of Modbus/TCP, and what’s more, it reaches the level of POWERLINK working in open mode.

Key words: Modbus/TCP;industrial Ethernet;μC/OS-II;real-time capability;token-ring