CAN總線技術(shù)及其在汽車(chē)中的應(yīng)用課件

1、CAN總線技術(shù)及其在汽車(chē)中的應(yīng)用網(wǎng)關(guān)PRND21!EFHCkm/hrpmTrip 000.0Odd 00000NEC儀表板胎壓檢測(cè)ABS雨刮控制無(wú)鑰匙登入電動(dòng)車(chē)窗CAN BUS自動(dòng)空調(diào)發(fā)動(dòng)機(jī)管理第1頁(yè)，共72頁(yè)。CAN Terminology Revealed.CAN 2.0 - Robert Bosch CAN Specification, Revision 2.0.CAN 2.0 A - Formerly CAN 1.2, limited to 11-bit identifiers.CAN 2.0 B - Usually means complete protocol standard -

2、 Including 11-bit and 29-bit identifiers第2頁(yè)，共72頁(yè)。CAN總線概述第3頁(yè)，共72頁(yè)。第4頁(yè)，共72頁(yè)。第5頁(yè)，共72頁(yè)。第6頁(yè)，共72頁(yè)。第7頁(yè)，共72頁(yè)。第8頁(yè)，共72頁(yè)。CAN-C (J2284)第9頁(yè)，共72頁(yè)。CAN應(yīng)用串行半雙工線性總線結(jié)構(gòu)通信CAN如何工作第10頁(yè)，共72頁(yè)。CAN不應(yīng)用物理地址的概念，而是采用在CAN信息中包含ID的形式；ID是編程時(shí)的符號(hào)CAN如何工作第11頁(yè)，共72頁(yè)。應(yīng)用中央控制器CAN控制器CAN收發(fā)器CAN總線獨(dú)立的CAN控制器低端集成的CAN控制器高端獨(dú)立的CAN控制器CAN硬件平臺(tái)CAN如何工作第12頁(yè)，

3、共72頁(yè)。ISO/OSI七層結(jié)構(gòu)CAN如何工作第13頁(yè)，共72頁(yè)。CAN與ISO/OSI七層結(jié)構(gòu)對(duì)比CAN如何工作第14頁(yè)，共72頁(yè)。CAN中“層”的作用CAN如何工作第15頁(yè)，共72頁(yè)。物理傳輸CSMA/CD機(jī)制顯性位競(jìng)爭(zhēng)獲勝CAN如何工作第16頁(yè)，共72頁(yè)。CAN如何工作第17頁(yè)，共72頁(yè)。CAN如何工作第18頁(yè)，共72頁(yè)。CAN數(shù)據(jù)傳輸采用包含位填充的NRZ編碼技術(shù)例子：CAN如何工作第19頁(yè)，共72頁(yè)。消息優(yōu)先級(jí)概念每一個(gè)消息都有一個(gè)ID，此ID用于選擇性接收CAN總線上的數(shù)據(jù)，以及訪問(wèn)不同消息的優(yōu)先級(jí)。CAN如何工作第20頁(yè)，共72頁(yè)。CAN仲裁機(jī)制：CAN如何工作第21頁(yè)，共72頁(yè)

4、。CAN協(xié)議和幀類(lèi)型CAN信息格式：第22頁(yè)，共72頁(yè)。CAN協(xié)議和幀類(lèi)型標(biāo)準(zhǔn)幀：11位ID第23頁(yè)，共72頁(yè)。CAN協(xié)議和幀類(lèi)型擴(kuò)展幀：29位ID第24頁(yè)，共72頁(yè)。CAN協(xié)議和幀類(lèi)型Example:數(shù)據(jù)幀（RTR0）遠(yuǎn)程幀（RTR1）錯(cuò)誤幀（連續(xù)6位電平相同）過(guò)載幀第25頁(yè)，共72頁(yè)。CAN協(xié)議和幀類(lèi)型遠(yuǎn)程幀和數(shù)據(jù)幀：第26頁(yè)，共72頁(yè)。CAN協(xié)議和幀類(lèi)型CAN控制場(chǎng)：第27頁(yè)，共72頁(yè)。CAN協(xié)議和幀類(lèi)型CAN數(shù)據(jù)場(chǎng)：第28頁(yè)，共72頁(yè)。CAN協(xié)議和幀類(lèi)型CRC場(chǎng)：CRC 場(chǎng) = 15 bit CRC 序列 + 1 位隱性界定符.發(fā)送 節(jié)點(diǎn)從發(fā)送的以下場(chǎng)來(lái)計(jì)算 CRC 值： SOF Ar

5、bitration Field Control Field Data Field (if present)所有接收節(jié)點(diǎn)從接收到的以下場(chǎng)計(jì)算 CRC 值 : SOF Arbitration Field Control Field Data Field (if present) 比較兩個(gè)CRC值.第29頁(yè)，共72頁(yè)。CAN協(xié)議和幀類(lèi)型應(yīng)答場(chǎng)：第30頁(yè)，共72頁(yè)。差錯(cuò)管理單元CAN節(jié)點(diǎn)的差錯(cuò)服務(wù)：差錯(cuò)檢測(cè)：CAN節(jié)點(diǎn)校驗(yàn)CAN總線上的信息是否滿足CAN標(biāo)準(zhǔn)；差錯(cuò)通知：每一個(gè)檢測(cè)到差錯(cuò)的CAN節(jié)點(diǎn)以錯(cuò)誤幀形式將差錯(cuò)信息 傳送給所有其他節(jié)點(diǎn)。差錯(cuò)處理：錯(cuò)誤記錄，并轉(zhuǎn)變?yōu)橐韵?種狀態(tài)之一： 主動(dòng)錯(cuò)誤 被動(dòng)

6、錯(cuò)誤 總線斷開(kāi)第31頁(yè)，共72頁(yè)。差錯(cuò)管理單元CAN節(jié)點(diǎn)的錯(cuò)誤類(lèi)型： 位錯(cuò)誤：發(fā)送和接收位不一致 填充錯(cuò)誤：一幀中出現(xiàn)多于5位同樣極性的電平 CRC錯(cuò)誤： ACK錯(cuò)誤： 格式錯(cuò)誤第32頁(yè)，共72頁(yè)。差錯(cuò)管理單元第33頁(yè)，共72頁(yè)。差錯(cuò)管理單元第34頁(yè)，共72頁(yè)。差錯(cuò)管理單元第35頁(yè)，共72頁(yè)。CAN實(shí)現(xiàn)第36頁(yè)，共72頁(yè)。CAN實(shí)現(xiàn)第37頁(yè)，共72頁(yè)。CAN收發(fā)器第38頁(yè)，共72頁(yè)。CAN收發(fā)器第39頁(yè)，共72頁(yè)。第40頁(yè)，共72頁(yè)。第41頁(yè)，共72頁(yè)。第42頁(yè)，共72頁(yè)。第43頁(yè)，共72頁(yè)。第44頁(yè)，共72頁(yè)。第45頁(yè)，共72頁(yè)。第46頁(yè)，共72頁(yè)。第47頁(yè)，共72頁(yè)。CAN Data Fr

7、ameNode start transmitting Data Frame after Inter-Frame Space (IFS).The two bus values are called dominant and recessive.All receivers synchronize to leading edge of Start Of Frame (SOF).Arbitration Field is 12 bits for a Std Format Data Frame (2.0A/B).Arbitration Field is 32 bits for a Ext Format D

8、ata Frame (2.0B).Bit Stuffing - whenever 5 consecutive bits of equal value are transmitted, 1 extra bit of complementary value is automatically inserted into the bit stream: provides edges for clock resynchronization. Receivers automatically unstuff.第48頁(yè)，共72頁(yè)。CAN Remote Transmission Request (RTR) Fr

9、ameA node is allowed to start transmitting a Remote TransmissionRequest (RTR) Frame after Inter-Frame Space (IFS).Similar to a Data Frame, but no Data Field.Interpreted as a request for data that is associated with theIdentifier in the Arbitration Field.Seldom used by automotive manufacturers.第49頁(yè)，共

10、72頁(yè)。數(shù)據(jù)幀中為顯性（0）遠(yuǎn)程幀中為隱性（1）標(biāo)準(zhǔn)幀中為顯性（0）擴(kuò)展幀中為隱性（1）第50頁(yè)，共72頁(yè)。替代遠(yuǎn)程請(qǐng)求位隱性（1）第51頁(yè)，共72頁(yè)。第52頁(yè)，共72頁(yè)。CAN Arbitration Field 2.0B (1)The 11-bit Identifier is labeled ID28 to ID18 in CAN2.0B.The Identifier is transmitted most significant bit (MSB) first.The 7 most significant bits of the Identifier must not all be re

11、cessive,per the CAN Specification.RTR bit : Dominant for Data Frame, recessive for RTR Frame.IDE bit : Dominant for a Standard Identifier.第53頁(yè)，共72頁(yè)。Arbitration Field 2.0B (2)The 11-bit Base Identifier is labeled ID28 to ID18.The 18-bit Extended Identifier is labeled ID17 to ID0.The Identifier is tra

12、nsmitted most significant bit (MSB) first.The 7 most significant bits of the Identifier must not all be recessive.SRR bit : Recessive for an Extended IdentifierIDE bit : Recessive for an Extended Identifier.RTR bit : Dominant for Data Frame, recessive for RTR Frame.第54頁(yè)，共72頁(yè)。CAN: Control FieldFirst

13、bit is called r1 in CAN2.0A, r1/IDE in CAN2.0B.First and second bits are always sent dominant.Data Length Code - number of data bytes for Data Frames (0-8 bytes).Data Length Code - no meaning for RTR Frames第55頁(yè)，共72頁(yè)。CAN Cyclic Redundancy Check (CRC) FieldCRC Field = 15 bit CRC Sequence + 1 recessive

14、 Delimiter bit.The transmitting node calculates the CRC from transmitted bit values of : SOF Arbitration Field Control Field Data Field (if present)All receiving nodes calculate the CRC from received bit values of : SOF Arbitration Field Control Field Data Field (if present) And compare this with th

15、e received CRC sequence.第56頁(yè)，共72頁(yè)。CAN Acknowledge FieldAcknowledge Field = ACK Slot bit + ACK Delimiter bitTransmitter transmits ACK Slot and ACK Delimiter as recessive.Receiver transmits a dominant bit during ACK Slot if it has received a valid message (no errors detected).Transmitter that does not

16、 receive dominant bit during ACK Slotrecognizes this as Acknowledge Error and will retransmit.第57頁(yè)，共72頁(yè)。 Intermission (3 recessive bits) No node is allowed to start transmitting a Data Frame or a RTR Frame during Intermission. BUT a dominant bit received during the 3rd bit time of Intermission will

17、be interpreted as SOF. ( Any error active node waiting to transmit which samples this dominant bit will synchronize to this edge and send the first bit of the Identifier at the next bit time. ) Suspend Transmit (8 recessive bits) Only for Error Passive nodes which transmitted the previous message Th

18、is node may not start to transmit during Suspend Transmit, but all other nodes may. Bus Idle (arbitrary number of recessive bits) The bus is free and any node may start a transmission.第58頁(yè)，共72頁(yè)。CAN Error DetectionBit Error - Detected by a transmitter if the bit value received is different from the b

19、it value transmitted.Exceptions:- sending a recessive bit and receiving a dominant bit during the Arbitration Field or the Ack Slot, or during a Passive Error flag. Stuff Error - Detected by a receiver if 6 consecutive bit values are received during a message field that should be encoded by bit stuffing. CRC Error - Detected by a receiver if the CRC calculated by the receiver is different from the CRC received in the CRC Sequence field. Form Error - Detected by a receiver if a fixed form bit field contains one or more illegal bits. Ac