The FlexRay electrical physical layer spec rev. 3.0.1 has been released. Mass production of the second generation of FlexRay transceivers according to that revision has started. Established silicon solutions will be gradually replaced by their successors. Whereas the conformity, compatibility, and interoperability of new products are taken for granted, the semiconductor manufacturers have to ensure full device specific functional range in existing applications as a drop-in replacement.
The goal of the second generation transceivers is to bring down costs without skipping currently required functionality. In terms of technological progress, new features are included.
Back in 2006 the first vehicle including a FlexRay network hit the road. A relatively low-risk platform for learning, understanding, and experiencing was the starting point. The mentioned automotive application is known as adaptive drive (by BMW), and surely it presented an important milestone for the new technology, made necessary for competing with established network systems, e.g. controller area networks (CAN), in automotive environments. The deterministic communication method of FlexRay was soon valued by the system architects, opening up new vistas for the design of chassis, powertrain, and safety-related applications.
To this day the number of car releases based on FlexRay electronic control units (ECUs) rises continuously. The system complexity regarding software, hardware, and network topology has increased. This fact profoundly conflicts with the cost pressure weighting down newly introduced technologies. However, today the car makers (OEMs) transfer their know-how to medium-sized and small car platforms, which clearly shows the degree of acceptance obtained for the bus system. Obviously this is one of the results of a close partnership between the OEMs, Tier-1 suppliers, and semiconductor manufacturers. The latter make sure to provide cost-optimized FlexRay transceivers according to the best available technology and most recent requirements.
Before FlexRay networks became ready for automotive series production, years of close cooperation of networking experts had taken place. In 2001 the FlexRay consortium was founded with access to broad know-how of automotive systems, including specialists from different domains like software, hardware, electromagnetic conformity, testing, and semiconductor manufacturers. The goal to release an open standard with defined system behavior, interfaces, and parameters was reached successfully in 2005 when the base for the first generation of FlexRay transceivers, called electrical physical layer (EPL) specification revision 2.1, was officially published.
According to the FlexRay definition, a compliant physical layer communication channel consists of four elements: bus driver (BD), twisted pair (TP) bus line, bus termination, and an active star (AS). The BD (transceiver) is an interface between the microcontroller (including the FlexRay communication controller) and the FlexRay bus. The bus driver converts the digital data stream to differential analog bus voltage and vice versa. The twisted pair bus line, with defined surge impedance, connects two or more bus nodes. The bus line is terminated by a resistor.
Usually an active star is placed in the center point of a FlexRay network. The active star can be used as a stand-alone device which redistributes the incoming bus signals to all other bus lines (branches). Optionally it can be used simultaneously as a signal router and a transceiver. In this case the locally transmitted data are sent to all FlexRay branches. All incoming data is mirrored at a single digital transceiver pin. This functionality is needed e.g. in network gateway applications.
Currently the FlexRay EPL specification revision 3.0.1 is available. Ten years after the formation of the FlexRay consortium, the second generation of FlexRay transceivers according to that specification release is in mass production. Therefore interoperability between 2.1 and 3.0 devices today, and for many years to come, is unavoidable. This applies to transceivers but also to the interaction between a communication controller and a bus driver which may be used in the same application.
The main goal during the definition process of the latest specification was to guarantee backward compatibility to EPL specification revision 2.1, a precise definition of active star parameters, and the best possible alignment to the physical layer parameter requirements of the Japan Automotive Software Platform and Architecture (JasPar) working group. This theoretical approach was refined by the test results of the actual silicon.
To read the complete article, which includes a migration to Rev. 3.0.1 analysis example and discussion of physical layer spec changes, click here, courtesy of EE Times Europe Automotive and Elmos Semiconductor.
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