A high performance token passing network for time critical applications

The Token bus network operating at 5 MBits/s has been successfully used in applications where response times in the order of 20 milliseconds are adequate. However, the Token Bus protocol also suffers from various forms of latent communication overheads. These overheads have the degrading effect of slowing down the network's response times. This inevitably leads to problems in hard real time applications where extremely fast network response times in the order of 2 milliseconds are required. This paper describes a novel technique of improving the response time of a token passing network without resorting to high transmission rates. A token passing network, known as the HRT-Net (Hard Real Time Network) operating at 1 MBits/s, is proposed and evaluated. It is shown that the HRT-Net provides superior response time characteristics when compared with other industrial standard networks like the Mini-MAP and the SAE High Speed Data Bus.