Development of a Class C Multiplex Control IC 930003
With the increasing use of electronic control systems to improve vehicle dynamics, there is an ever growing need to transfer control information among electronic control units(ECUs). To meet this need, a protocol was proposed for high-speed multiplex in the previous SAE paper 910463. Based on the paper, a prototype IC for high-speed multiplexing control was developed.
First, a further analysis was made of the information which is transferred among ECUs. As a result, it was found that the information has certain distinctive characteristics. These characteristics are so distinctive that it may be relevant to devise a new protocol for communication.
Based on the analysis, a new form of token passing method was implemented. By using this method, it is easy to calculate transmission latency time. So this method is suitable for a real time control application like vehicle dynamics control.
Another key point of high-speed data communication is the extent of load imposed upon the host microprocessor. Although a serial communication interface was used, by using methods of ID filtering, ID sorting, and DMA, the load on the microprocessor was made very light.