SPECIAL EDIT ION FLEXRAY lA U T O M O T I V E 2 0 0 7 l29

FlexRay Controller -Integrated or Discrete?

A utomotive system designers require acombination of performance, flexibility,cost effectiveness, scalability and safe-

ty that is sometimes hard to reach. A fully inte-grated solution can be cost effective but requi-res a whole new system design.While designs have more pressure on space,using a discrete solution can take more space butprovides the potential to upgrade the system easi-ly. This also allows developer to use a range of dif-ferent processors, both within a family of devices,re-using the same software, but also across diffe-rent families for different applications, from cars tohigh end motor cycles. A key example of this comes from using the Flex-Ray communications protocol. Version 2.1 of thespecification has been available for several yearsnow, but the devices that support the new stan-dard have taken time to come to the market. Oneof the first was the CIC310 stand alone FlexRaycommunication controller, which has been quali-fied in many designs, but now this same designhas been integrated into the TC1797 TriCore 32-bitcontroller (Figure 1). This allows system integra-tors to build fully FlexRay v2.1 compliant in-vehiclenetworks for powertrain, chassis and body appli-cations.The FlexRay controller core is based on the wide-ly used E-RAY design from system supplier Boschand is integrated into the TC1797, part of the AUDOFUTURE microcontroller family. This family usesthe high performance 32-bit TriCore processor core thatcombines microcontroller functions with digital signal pro-cessing and the industry’s highest density flash memory. The family includes a wide range of peripherals such as afast ADC, DMA memory engine and several serial interfa-ces and external bus Interfaces. Most of the family also hasan additional 32-bit Peripheral Control Processor (PCP) onboard that offloads the main CPU by running the low-leveldrivers for the integrated peripherals. The previous TC1796 recently achieved a score of 100 Auto-mark in the certified EEMBC Benchmark (http://www.eembc.org/) – the highest score for an automotive

qualified microcontroller in this frequency range. TheTC1797 adds another 30% system performance with its Tri-Core operating at 180 MHz.This level of performance and integration is aimed at highend engine control units (ECUs) to handle the complexalgorithms for emission control and FlexRay is mandatoryin current and future designs of these systems (Figure 2).

Discrete: The flexible way

At the same time there can be advantages from using adiscrete controller. The CIC310 is a standalone FlexRayV2.1 Protocol Controller based on the same Bosch IP and

What are the advantages for

automotive system designers

of using a discrete FlexRay

communications controller and

one integrated into its high end

32-bit microcontroller family

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30 lA U T O M O T I V E 2 0 0 7 lS P E C I A L E D I T I O N F L E X R AY

has already passed the mandatory FlexRay ConformanceTest. It is partnered with a microcontroller or microproces-sor via a standard interface and allows designers to provi-de FlexRay as an optional feature that can be easily inte-grated into an existing hardware and software design. Inthis case, the footprint for the CIC310 and the accordingFlexRay transceiver will be available on printed circuit boardbut the devices will be only mounted if needed, and thisalso provides an upgrade path for existing systems.

The controller supports both FlexRay communication chan-nels with a maximum bandwidth of 10 Mbit/s each and pro-vides 8.25 KBytes of configurable message RAM for sto-ring up to 128 messages. The redundancy of the two inde-pendent communication channels, along with the FlexRaytime-triggered communication schemes and high band-width are key for safety critical automotive applications. Low power is also a key feature of the CIC310. Manufac-tured in a 130 nm process technology, the core consumes30 mA to 50 mA. To support designers, a number of hardware features areimplemented. Eight independent DMA channels offer anefficient transfer mode without using the host CPU. Seve-ral interrupt lines give full control of the CIC Channel HostInterface (CHI) and the E-RAY communication controller,and this provides three different interfaces (Figure 3): A low pin count SPI (Serial Peripheral Interface) interfacesupporting up to 20 MBaud BandwidthA configurable 8/16-bit wide bus parallel interface includinga 13 Bit address bus (with address extension mechanismto 32-bit) supporting up to 10 MByte/sec bandwidthA high speed serial MLI (Micro Link Interface) supportingup to 40 MBaudThis flexible channel host interface means the CIC310 canbe used with almost any microcontroller or microproces-sor architecture available in the market. The new TC1767 and TC1736 TriCore controllers do not haveintegrated FlexRay and provide a path for more cost optimi-sed designs from the TC1797 using the same software. Bothintegrate the same microcontroller core as TC1797, the same

built-in safety features like a Memory Protec-tion Unit (MPU) and a software-compatibleperipheral set. In addition to powertrain appli-cations, the TC1767 and TC1736 can also beused in safety critical application in chassiscontrol area like high-end sensor clusters andsuspension.To connect the TriCore to the CIC310, all threeinterface options available can be used. Themost efficient interface is using the MicroLink Interface (MLI) as this provides synchro-nous high-speed serial connection for auto-matic data transfer/request transaction bet-ween a local and a remote controller. It alsosupports transparent read/write access witha low pin count. For the connection between the processorand the Companion IC only eight pins arenecessary - four each for transmit and recei-ve. Further pins are available for additionalinterrupt lines to monitor both the ERAY Con-troller and the CIC310. As the TriCore internal bus structure supportsthe DMA capability of the CIC310 via MLIinterface, the FlexRay communication is sup-ported with minimum performance require-ment from the main TriCore CPU. Other inter-nal DMA operations can also be offloaded tothe on-chip 32-bit peripheral controller.

Figure 1:The TC1797 uses a new high performance 32-

bit TriCore CPU that combines microcontroller functions

with digital signal processing and the industry’s hig-

hest density flash memory.

© automotive

Figure 2:The TC1797 microcontroller is optimized for engine management

systems and transmission. In engine management, the TriCore provides lower fuel

consumption and improved emissions.With a number off build-in safety features

like a Memory Protection Unit (MPU) the TriCore is also a fit for safety critical

application in chassis control area like high-end sensor clusters and suspension.

© automotive

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SPECIAL EDIT ION FLEXRAY lA U T O M O T I V E 2 0 0 7 l31

Well supported

The discrete controller is not just applicable to the TriCorefamily. The latest XC2200, XC2300 and XC2700 families ofcontrollers are based on the Infineon’s C166S V2 micro-controller architecture and can all make use of the discre-te FlexRay controller.The XC2200 is designed for body applications like BodyCentral Module, Central Gateway and air-conditioning withpower consumption in standby down to 50 uA as well asextended communication capabilities. The XC2300 familycovers applications in the safety critical area like airbag andElectronic Power Steering (EPS) by adding Error CorrectionCode (ECC) on all memories, memory protection, a CRC(Cyclic Redundancy Check) and redundant analog-digitalconverters, and supports systems to be certified inIEC61508 level SIL3. The XC2700 32-bit microcontrollersare optimised for Engine Management and allow systemmakers to build cost-effective electronic engine control inmotorcycles around the world to meet upcoming emissionstandards.Interfacing the XC2200, XC2300 and XC2700 to the CIC310can be either through the standard 8- /16-bit parallel businterface or through one of the incorporated USIC’s (Uni-versal Serial Interfaces). These support the fast SPI stan-dard, running a bandwidth of up to 20 Mbit per second bet-ween the CIC310 and the microcontroller. In applicationswith critical latency requirements, the parallel interface isthe recommended solution as it supports a speed of up to10 MByte per second with very low latency impact.But implementation is also an important issue for desi-gners, so AUTOSAR software drivers for the CIC310 areavailable and have already been proven by the AUTOSARValidator project. At the same time, the TriCore family aswell as the XC2200, XC2300 and XC2700 families are sup-ported by a full suite of development tools including evalu-ation boards, debuggers, compilers and documentation.Automotive equipment makers are already using FlexRay

in series production, and broad introduction is plan-ned already in 2009. This means a wide range ofdifferent solutions will be required by the equip-ment makers, all based around FlexRay as thecommunications controller. Having both integrated, tightly coupled implemen-tations such as the TC1797 and the discrete

CIC310 allows the system design to select the right pro-cessor core for the application and still easily provide Flex-Ray communications. The discrete approach also providesa simple upgrade path for today’s designs to become Flex-Ray-enabled.

Figure 3: Infineon’s Channel Host Interface (CHI) Concept for the

CIC310 supports 3 different options: a standard parallel interface,

a Serial Peripheral Interface (SPI) and a High Speed Serial Micro

Link Interface (MLI)© automotive

Kai Konrad (l.) is Product Marketing Manager for Microcontrollers Automotive at Infineon Technologies, and Holger Huber (r.) is ProductMarketing Manager for Microcontrollers Automotive at Infineon Technologies

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