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1、INTERFRAMEINTERFRAME 1INTERFRAMESPACE：separateDATAFRAMEsandFRAMEsfromprecedingframeswhatevertypetheyare(DATAFRAME, REMOTE FRAME, ERROR FRAME, OVERLOAD FRAME)2OVERLOADFRAMEsandERRORFRAMEsarenotprecededbyan INTERFRAME SPACE（在overload 和error之前沒有interframe）3multipleOVERLOADFRAMEsarenotseparatedbyanINTER

2、FRAME INTERFRAMEINTERFRAME 1 INTERFRAME SPACE INTERMISSION（間歇） BUS IDLEINTERFRAMEINTERFRAME ForerrorpassivestationswhichhavebeenTRANSMITTERofthe previous message:增加了SUSPEND TRANSMISSION（掛起傳送INTERFRAME 1consistsofthreerecessive2DuringINTERMISSIONtheonlyactiontobetakenissignallingan OVERLOAD condition

3、（看是否第一或第二位為dominent）3nostationisallowedtoactivelystarttransmissionofaDATAFRAMEor REMOTE FRAME.4 注意：If a CAN node has a message waiting for transmission and it samples a dominant bit at the third bit of INTERMISSION, it will interpret this as a START OF FRAME bit, and, with the next bit, start transm

4、itting itsmessagewiththefirstbitofitsIDENTIFIERwithoutfirsttransmittinga START OF FRAME bit and without becoming receiver.BUSBUS INTERFRAME 1TheperiodofBUSIDLEmaybeofarbitrary2Thebusisrecognizedtobefreeandanystationhavingsomethingto transmit can access the bus.3Amessagewhichispendingfortransmissiond

5、uringthetransmissionof another message(suspend transmission), is started in the first bit following INTERMISSION.4ThedetectionofadominantbitonthebusisinterpretedasaSTART OF FRAME.SUSPENDSUSPEND INTERFRAME k1SUSPENDeightrecessive2 After an error passive station has transmitted a message, it sends eig

6、htrecessivebitsfollowingINTERMISSION,beforestartingtotransmit a further message or recognizing the bus to be idle.3Ifmeanwhileatransmission(causedbyanotherstation)starts,the station will become receiver of this message.被動錯誤節(jié)點(diǎn)，B報文優(yōu)先級高于AB獲取總線控制權(quán)，第Definitionof TRANSMITTER / 1 A unit originating a messa

7、ge is called “TRANSMITTER” of that message.TheunitstaysTRANSMITTERuntilthebusisidleortheunit loses ARBITRATION.2 Aunitiscalled“RECEIVER”ofamessage,ifitisnotTRANSMITTER of that message and the bus is not idle.MessageMessagefilteringisbasedthewholemaskMESSAGE 1 Message filtering is based upon the whol

8、e Identifier. Optional mask registers that allow any Identifier bit to be set dont care for message filtering,maybeusedtoselectgroupsofIdentifierstobemappedintothe attached receive buffers.2 If mask registers are implemented every bit, mask registers must be programmable(可編程的), i.e. they can be enab

9、led or disabled for messagefilteringThelengthofthemaskregistercancomprise(包含the whole IDENTIFIER or only part of it.MESSAGEMESSAGE 70f3239單片機(jī)的CAN控制器的ID寄存器MESSAGEMESSAGE Thepointoftimeatwhichmessage is taken to be valid, is different for the transmitter and the receivers of the message.MESSAGE 1Theme

10、ssageisvalidforthetransmitter,ifthereisnoerroruntil the end of END OF FRAME.Ifamessageiscorrupted,retransmissionwillfollowautomatically and according to prioritization. In order to be able to compete for bus access with other messages, retransmission has to start as soon as the bus is idle.2Themessa

11、geisvalidforthereceiversifthereisnoerroruntil thelastonebitofENDOFFRAME（除了幀末尾位）Thevalueofthe last bit of END OF FRAME is treated as dont care, a dominant value does not lead to a FORM ERROR (cf. section 7.1).范圍：TheframesegmentsSTARTOFFRAMEARBITRATIONFIELD, CONTROL FIELD, DATA FIELD and CRC SEQUENCE

12、are coded by the method of bit stuffing.規(guī)則1：Wheneveratransmitterdetectsfiveconsecutivebitsofidentical value in the bit stream to be transmitted it automatically inserts a complementary bit in the actual transmitted bit stream.規(guī)則2：The remaining bit fields of the DATA FRAME or REMOTE FRAME(CRCDELIMITE

13、RACKFIELDandENDOFFRAMEareoffixedformandnot規(guī)則3TheERRORFRAMEandtheOVERLOADFRAMEareoffixed form as well and not coded by the method of bit stuffing.規(guī)則4The bit stream in a message is coded according to the Non- Return-to-Zero(NRZmethodThismeansthatduringthetotalbittimethe generated bit level is either d

14、ominant or recessive.無0態(tài)。Wheneverthebusisfree,anyunitmaystarttotransmitaIf2ormoreunitsstarttransmittingmessagesatthesametime,thebus access conflict is resolved by bitwise arbitration using the IDENTIFIER.During arbitration every transmitter compares the level of the bit transmittedwiththelevelthatismonitoredonthebus.Iftheselevelsare equaltheunitmaycontinuetosend.Whenarecessivelevelissentand a dominant level is monitored (see Bus Values), the unit has lost arbitration and must withdraw without sending one