Today vehicles include an increasing number of electronics systems. It has been estimated by Dataquest that the average semiconductor content of a vehicle will reach $240 by 2001, with consumption of DSPs, microcontrollers and microprocessors reaching $4.9 billion. Typical configurations consist of interconnected Electronic Control Units (ECUs) which may be connected through several buses. One possible bus is the "entertainment/infotainment" bus which connects subsystems such as radio, telephone, and navigation. Another one is the control bus which connects ECUs such as the ABS, the engine control, or the transmission control subsystem. A vehicle such as the Volvo S80 includes "18 ECUs connected via six networks: a low-speed body electronics CAN bus (125kbit/s), a high-speed powertrain CAN bus (250kbit/s), and four other networks."
ECUs are part of an embedded system market which is very fragmented since it ranges from systems based on 4 bit microcontrollers (e.g. a light switch) to 128 bit processors (e.g. game consoles). Today 4 to 16 bit microcontrollers make up the bulk of the market in terms of volume (around $10 billion per year or higher), while 32 bit and higher systems count for less than 10% of the market. It is however expected that 32 bit systems will expand at a much higher rate than 16 or 8 bit microcontrollers.
Most ECUs in the automotive control systems market are currently 8 to 16 bit systems. An increasing number of 32 bit systems will be included in the next generation of vehicles, but for cost and reliability reasons, such systems are likely to be designed using single chip or system on a chip approaches. This implies significant constraints in acceptable memory footprints.
ECUs often have to deal with duty cycles of several ms. Engine control subsystems for instance have to manage the engine cycle which has a duration that depends on the round per minute (RPM). At 6000 RPM, the engine cycle is 20 ms, which means that the ECU has to handle timing constraints on the order of several ms. In addition, ECUs exchange control data through the bus. The exchange period can be as low as several ms. The CAN bus is a typical type of control bus currently in use. Note that in many cases, engineering decisions made by OEMs may add further real-time constraints, such as the implementation of a serial link or a multiplexing link by software to lower cost.
ECUs are typically designed and developed by OEMs according to requirements set up by car manufacturers. Such requirements include a detailed description of expected interfacing capabilities, and in particular a detailed description of data transmitted to the ECUs or to be transmitted by the ECUs. In many cases, OEMs are not informed of the entire vehicle message system, as the car manufacturer may wish to protect trade secrets.
Until quite recently OEMs had in most cases total freedom in the design of ECUs, including the software, the processor and the hardware. However car manufacturers now anticipate a need to provide very precise requirements, in particular at the software level. There is a trend toward the specification of more global functions made possible by the networking and multiplexing capabilities of todayís vehicles, for example an automatic gear shift function could sit partly in the transmission control ECU and partly in the engine control ECU. Thus a car manufacturer may wish to subcontract an OEM for the development of only the software component (e.g. the global gear shift function or the part sitting in the engine control) or for the production of an incomplete ECU (e.g. the engine control part without the automatic gear shift part). This approach not only allows the implementation of global functions, but it can also further protect the car manufacturers trade secrets.
To address this trend, the automotive industry is looking for technologies that will facilitate the software development integration process. It has identified the need to provide guidance on the transition towards advanced electronic architectures in the following ways:
Java could be the cornerstone technology on which the infotainment bus could be built. The AMIC initiative (www.ami-c.com) on multimedia interoperability, created in October 1998 by five leading manufacturers (GM, Ford, DaimlerChrysler, Toyota, Renault) which now includes all car manufacturers, is investigating an open technology in the multimedia area based on Java.
On the other hand, Java has not yet been considered for automotive control systems because of technology issues, like memory footprints and real-time.
‘ Java is a trademark of Sun Microsystems
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