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Features and applications of the new generation of vehicle mounted network FlexRay 1. Introduction the FlexRay vehicle mounted network standard has become the benchmark of similar products and will guide the development direction of the control structure of the entire automotive electronic products in many years to come. FlexRay is the latest research and development achievement after can and Lin, which can effectively manage multiple safety and comfort functions: for example, FlexRay is suitable for X-by-wire operation

this technical background report gives us a general introduction to the application of FlexRay in the vehicle network, and describes its network protocol, including frame format, topology, bus signal and node state transition. The report also compares FlexRay and can, and finally adds information about FlexRay chips and the development support of Fujitsu Microelectronics USA. Based on the license of Bosch, Fujitsu has launched FlexRay starter kit and FlexRay controller application standard product (ASSP)

flexray is a registered trademark of DaimlerChrysler Corporation. FlexRay consortium has promoted the standardization of FlexRay, making it a new generation of automotive internal network communication protocol. Fujitsu group is an associate member of FlexRay alliance and a full member of AUTOSAR (Automotive open system architecture organization) and Jaspar (Japanese automotive software platform and Architecture)

II. FlexRay's advantages

flexray focuses on some core requirements of today's automotive industry, including faster data rate, more flexible data communication, more comprehensive topology selection and fault-tolerant operation

therefore, FlexRay can provide the required speed and reliability for the next generation of in car control systems. The maximum performance limit of can network is 1Mbps. The maximum data rate on the two channels of FlexRay can reach 10Mbps, and the total data rate can reach 20mbit/S. therefore, when applied to the vehicle network, the network bandwidth of FlexRay may be as much as 20 times that of can

flexray can also provide many reliability features that can networks do not have. In particular, the redundant communication capability of FlexRay can completely copy the network configuration through hardware and monitor the progress. FlexRay also provides flexible configurations that support various topologies, such as bus, star, and hybrid topologies (see Figure 1). Designers can configure distributed systems by combining two or more topologies of this type

in addition, FlexRay can carry out synchronous (real-time) and asynchronous data transmission to meet the needs of various systems in the vehicle. For example, distributed control systems usually require synchronous data transmission

in order to meet different communication requirements, FlexRay provides static and dynamic communication segments in each communication cycle. The static communication segment can provide bounded delay, while the dynamic communication segment helps to meet the different bandwidth requirements during the system operation time. The fixed length static segment of FlexRay frames uses the fixed time trigger method to transmit information, while the dynamic segment uses the flexible time trigger method to transmit information

flexray can not only operate as a single channel system such as can and Lin network, but also as a dual channel system. Dual channel system can transmit data through redundant network, which is also an important performance of highly reliable system

as shown in Table 1, various features of FlexRay are suitable for real-time control. Among the various networking protocols listed in the table, FlexRay has the most outstanding performance. Figure 2 further compares various network standards in terms of node cost and data rate. In Table 2, FlexRay and can are compared in detail

special engineering plastics will be a highlight in the meeting

note: mixed crosstalk: wrong transmission leading to damage; BG: bus monitor; CC: communication controller; BD: bus driver

III. application of FlexRay

as shown in Figure 3, FlexRay is oriented to many in car wired operations (X-by-wire). The figure also shows a switch that combines FlexRay and can networks

examples of FlexRay wire control applications include:

· steering by wire - typically using electronic control units

· anti lock braking system (ABS) - including vehicle stability control (VSC) and Vehicle Stability Assistant (VSA)

· powertrain - replacing existing mechanical systems to control electronic throttle. The electronic throttle works in combination with existing systems, such as computerized fuel injector, computerized variable intake system and computerized idle speed control system

1. FlexRay node operation

each FlexRay node includes a controller and a driver component (see Figure 4). The controller component includes a host processor and a communication controller. Drive components usually include bus drivers and bus monitors (optional). The bus driver connects the communication controller with the bus, and the bus monitor monitors the connection to the bus. The host notifies the bus monitor that the communication controller has allocated those time slots. Next, the bus monitor only allows the communication controller to transmit data in these slots and activate the bus driver. If the bus monitor finds an interval in the time sequence, disconnect the communication channel

as shown in Figure 5, FlexRay's nodes have several basic operating states:

· configuration state (default configuration/configuration) - used for various cooperative point settings for initial identification of civil military integration, including communication cycle and data rate

· ready state - used for internal communication settings

· wake up State - used to wake up nodes that are not communicating. In this state, the node sends a wake-up signal to another node to wake up and activate the communication controller, bus driver and bus monitor

· start status - used to start clock synchronization and prepare for communication

· normal state (active/passive) - the state in which communication can be carried out

· interrupt state - indicates that communication is interrupted

flexray nodes also have state transitions related to error handling. These transitions are managed based on the value of the error counter for clock synchronization and clock correction errors. When the clock of an individual node is different from that of the FlexRay synchronization node, a clock correction error will occur. FlexRay network has one or more synchronization nodes that transmit synchronization information. After receiving any synchronization information, the node will compare its clock with the clock of the synchronization node and make necessary changes according to the synchronization needs

each node should count errors, including the number of consecutive errors in clock synchronization. At the same time, the node also monitors the errors related to the frame transfer/acceptance status, including syntax errors, content errors, bus interference errors and errors caused by transfer conflicts. Once a node finds such errors, it will notify the host processor. The use of error counters depends on the application purpose and system design. For example, the node can interrupt communication according to the error condition

2. The communication frame used by FlexRay frame and signal

flexray has three frame segments. (see Figure 7)

unlike the event trigger protocol of can network, FlexRay uses time trigger protocol to transfer frames. FlexRay's time triggered mode ensures that data is transmitted according to a predetermined schedule. In addition, both ACh and BCH can transmit data


header includes the following bits:

· reserved bits - prepare for future expansion

· load segment preamble indication - indicates the vector information of the load segment of the frame. In a static frame, this bit indicates nwvector; In dynamic frames, This bit indicates the information ID

· zero frame indication - indicates whether the data frame of the load segment is zero

· synchronous frame indication - indicates that this is a synchronous frame

· start frame indication - indicates whether the node sending the frame is the start frame

· frame ID - indicates the ID allocated to each node in the system design process (effective range: 1 to 2047)

· length - describes the data length of the load segment

· header CRC - indicates the CRC calculated values of the synchronization frame indicator and the start frame indicator, as well as the frame ID and frame length calculated by the host

· period - indicates the cycle count of the node transmitting the frame within the frame transmission time

the load segment of the frame includes three parts:

· data - can be 0 to 254 bytes

· information ID - arbitrary. This information ID is defined by the first two bytes of the load segment and can be used as filterable data at the receiver

· network management vector (nwvector) -- any. The vector must be 0 to 10 bytes long and the same as all nodes

the end of the frame includes the CRC value specified by the hardware. These CRC values will change the seed value on the connected channel to prevent incorrect correction. FlexRay transmits frames in time slots. Figure 8 shows the composition of the time slot related to the FlexRay cycle

in the physical layer, FlexRay uses different signals BP and BM to communicate according to different voltages of Ubp and UBM. The four signals (see Figure 9) represent various states of the FlexRay bus:

· idle_ LP: low power state

· idle: no communication state

· data_ 1: Logic high

· data_ 1: Logic low

note in data_ 1 and data_ No conflict is allowed between 0

IV. the FlexRay solution provided by Fujitsu Microelectronics

after several years of improvement, the FlexRay network standard has matured, and system developers can apply the standard in the new generation of vehicles. Fujitsu has developed a development system and microcontroller with FlexRay IP. Figure 10 shows the roadmap of the development process

Fujitsu's new FlexRay Starter Kit (sk-91f467-flexray) ensures that designers can evaluate Fujitsu's independent FlexRay controller (mb88121a) and Fujitsu's 32-bit flash microcontroller mb91f467da. The kit includes the decomsys:: commstack driver library, which ensures easy access to the FlexRay communication controller mb88121a. The kit includes the following parts:

· 32-bit flash microcontroller mb91f467da

· FlexRay application standard product mb88121a

· two FlexRay channels (channel a, channel B)

· physical layer RS485 on FlexRay board

· FlexRay physical layer plug-in (ft1080) for PL module of TZM

· static random access memory on 32 Mbit board

· three high-speed can interfaces

.· three universal asynchronous receiving/transmitting devices (UART) ((configurable rs232- or Lin mode)

· external bus interface on 96 pin/48 pin connector (DIN 41612) for users

· application example on FlexRay CD

· soft workbench development environment on CD

· demo CD of decomsys tool chain

Fujitsu also provides FlexRay application-based standard products that support FlexRay protocol version 2.1 (ES2). This application-oriented standard product has the following characteristics:

· qfp64

· 0.5 pin spacing/10 x 10 mm

· single voltage

· clock specification, 4/5/8/10 MHz crystal oscillator

· configurable parallel host interface, which is compatible with 8-bit, 16 bit and 32-bit microcontrollers, and the maximum frequency is 33MHz (target)

· serial host interface (future devices will be supported)

2006, Fujitsu will launch two FR series 32-bit microcontrollers with integrated FlexRay. Figure 13 shows some features of the first MCU of this kind. Figure 14 shows the second one with more on-board peripheral functions


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