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In order to expand the applicable range of in-vehicle LANs down to popular cars, drastic cost reduction is essential. In addition, an in-vehicle LAN with high transmission rate and advanced functioning is extremely important for the further spreading of vehicle electronics intended to enhance vehicle intelligence. We developed the Protocol for Automotive Low and Medium Speed Network (PALMNET) as an in-vehicle LAN system and put it into practical use in 1990. Based on this, we developed a new communication protocol and three ICs for an in-vehicle LAN called the Advanced Protocol for Automotive Local Area Multiplexing Network (Advanced PALMNET), which satisfies the above-mentioned requirements and covers the medium-to-low transmission rate (up to 125kbps) to high rate (up to 1Mbps).

The on board multiplexing communication system is regarded as a necessary technology for the future of electronics in automobiles. Many companies are developing multiplexing systems, and the ISO and SAE have been active in establishing standards for communication protocols. The proposed communication protocols have different specifications. Consequently, no compatible evaluation standards exist, so it was difficult to compare one protocol to another. Therefore, to assist the standardization activities of the ISO and SAE, we have developed an evaluation method for distributed multiplexed communication systems and have evaluated each of the proposed protocols using this method. These evaluations were performed from the point of view of the future users of these systems. In this paper we present the results of the experiments on eight distributed multiplexed communication systems, each of which consists of a communication IC and the proposed physical layer.

While basic automobile performance is improving along with the growth of higher value-added features, rapidly increasing use of electrical and electronics systems with complex wire harnesses is becoming a problem. This is bringing the automotive distributed control multiplex system to commercial reality. At present, standardization of protocols is under deliberation by SAE and ISO, and several protocols are being considered as candidates. To select a multiplex LSI having an optional protocol, we have established a method to evaluate automotive distributed control multiplex system from the standpoint of users. The method will permit comparison of various multiplex LSIs including physical layers and their protocols' performance/reliability, while helping clarify their features and areas of applications. It is our hope that through this activity of ours, we will be able to make some contribution to global standardization in the field.

On board multiplexing communication system is regarded as a necessary technology for the future of electronic system in automobiles. Many companies are developing multiplexing systems and the ISO and SAE are active in establishing standards for communication protocols. The proposed communication protocol specifications have different specifications. Consequently, no compatible evaluation standards existed, and it was difficult to compare one protocol to another. Therefore, to assist the standardization activities of the IS0 and SAE, we have developed an evaluation method for distributed multiplexed communication systems and evaluated each of the proposed protocols using this method. These evaluations were performed from the point of view of the future users of these systems. In this paper we present the results of the experiments on distributed multiplexed communication systems each of which consists of communication IC and the proposed physical layer.

At present, various communication protocols for an automotive distributed control multiplex system that aims at solving wire complexity and meeting the requirements of high reliability and open system flexibility have been proposed and installed in production cars. The requirements for an automotive distributed multiplex system, especially reliability, flexibility, and economy have been analyzed in detail, and as a result a new communication protocol based on SAE J-1850 has been developed. This paper describes the design philosophy and technical features of the protocol, named PALNET (Protocol for Automotive Local area Network) and the result of evaluation with the experimental system. PALNET covers moderate speed signals in vehicle electrical and electronic system. Main technical features of PALNET are as follows. Introduction of a new acknowledgement method named ANC (Acknowledgement for Network Control) secures high reliability of data communication.