INTERNATIONAL STANDARD ISO 11898-1 Second edition 01 5-1 -1 Road vehicles — Controller area network (CAN) — Part : Data link layer and physical signalling Véhicules routiers — Gestionnaire de réseau de communication (CAN) — Partie : Couche liaison de données et signalisation physique Reference number ISO 1 898-1 : 01 (E) I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © ISO 01 ISO 11898-1:2 015(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2015, Published in Switzerland All rights reserved Unless otherwise speci fied, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country of the requester ISO copyright office Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © ISO 2015 – All rights reserved ISO 11898-1:2 015(E) Contents Page Foreword vi Introduction vii Scope Conformance Normative references Terms and de initions f Symbols and abbreviated terms Basic concepts of CAN 6.1 CAN properties 6.2 Frames 6.3 B us access method 6.4 I nformation routing 6.7 Remote data request 6.8 E rror detection 6.1 ACK 6.1 Automatic retransmission 6.1 E rror-active 6.1 E rror-passive 6.1 B us-off 6.5 6.6 6.9 6.12 Network flexibility Data consistency Error signalling and recovery time Fault finement Layered architecture of CAN 10 7.1 Reference to O SI model 7.3 Format description of services 1 7.2 Protocol speci fication 1 7.3.2 7.4 Types of service primitives LLC interface Description of LLC sub-layer 12 8.1 8.2 8.3 General Services of LLC sub-layer 8.2.1 Types of connectionless-mode transmission services 8.2.2 Service primitive speci fication Functions of LLC sub-layer 8 8.3.2 8.3.3 8.3.4 8.4 8.4.2 8.4.3 8.5 General Frame acceptance filtering Overload noti fication Recovery management Structure of LLC frames 9 Format description of service primitives 1 General Speci fication of LLC DF Speci fication of LLC RF Limited LLC frames Interface between LLC and MAC Services Time and time triggering 9.2 D escription 9.2 Time base 9.2 Time reference point © I SO – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n iii ISO 11898-1:2 015(E) 9 9 10 Event generation 2 D isabling automatic retransmission 2 Retransmission of frames 2 M essage time stamping 2 Description of MAC sub-layer 2 1 10.2 General 2 Services of MAC sub-layer 10.3 22 Service description 2 10.2.2 Service primitives speci fication Functional model of MAC sub-layer architecture 10.3.1 Capability 23 27 27 Frame transmission 3 Frame reception Structure of M AC frames 4.1 10.4.2 10.4.3 10.4.4 10.4.5 10.4.6 D escription Speci fication of MAC DF Speci fication of MAC RF Speci fication of EF Speci fication of OF Speci fication of inter-frame space 29 34 34 35 36 Frame coding Frame acknowledgement 7 Frame validation O rder of bit transmission M edium access method 9 General 9 M ulti-master 9 B us access 40 B us integration state 40 Protocol exception event 40 Transmission of M AC frames 40 Content-based arbitration 40 9 Collision resolution 41 10.9.8 Frame priority 41 D isabling of frame formats 41 10.10 MAC data consistency 41 E rror detection 41 1 E rror signalling 42 1 O verload signalling 43 1 B us monitoring 44 1 Restricted operation 44 1 General and functional modelling 44 1 Services of PL 44 11 PL speci ication f 11.3 11.4 iv 1 44 1 D escription 44 1 2 PCS_D ata.Request 45 1 PCS_D ata.I ndicate 45 1 PCS_Status.Transmitter 45 1 PCS_Status.Receiver 45 1 B it encoding/decoding 45 PCS speci fication 11.3.2 Synchronization 11.3.3 Transmitter delay compensation AUI speci fication 45 50 52 54 1 4.1 General 1 4.2 PCS to PM A messages 5 1 4.3 PM A to PCS message 5 I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © I SO – All rights reserved ISO 11898-1:2 015(E) 12 Description of supervisor FCE 55 12.1 Fault finement 5 1 Obj ectives 5 2 Strategies 5 Network start-up 60 12.1.3 12.1.4 2 Fault finement interface speci fication Rules of fault finement Bus failure management 60 Annex A (informative) Additional Information 61 Bibliography 65 © ISO 01 – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n v ISO 11898-1:2 015(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work of preparing International Standards is normally carried out through ISO technical committees Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the different types of ISO documents should be noted This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso.org/directives) Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights ISO shall not be held responsible for identifying any or all such patent rights Details of any patent rights identi fied during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement For an explanation on the meaning of ISO speci fic terms and expressions related to conformity assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers to Trade (TB T) , see the following URL: Foreword — Supplementary information The committee responsible for this document is ISO/TC 22 , communication Road vehicles, Subcommittee SC 31, Data This second edition cancels and replaces the first edition (ISO 11898-1:2003), which has been technically revised It also incorporates the Corrigendum ISO 11898-1: 2003/Cor 1: 2006 ISO 11898 consists of the following parts, under the general title network (CAN) : Road vehicles — Controller area — Part 1: Data link layer and physical signalling — Part 2: High-speed medium access unit 1) — Part 3: Low-speed, fault-tolerant, medium-dependent interface — Part 4: Time-triggered communication — Part 5: High-speed medium access unit with low-power mode 1) — Part 6: High-speed medium access unit with selective wake-up functionality 1) 1) Parts 2, 5, and are being revised They will be merged under a new edition of Part vi I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © ISO 01 – All rights reserved ISO 11898-1:2 015(E) Introduction ISO 11898 was first published as one document in 1993 It covered the CAN data link layer, as well as the high-speed physical layer In the reviewed and restructured ISO 11898 series: — Part de fines the data link layer including the logical link control (LLC) sub-layer and the medium access control (MAC) sub-layer, as well as the physical signalling (PHS) sub-layer; — Part de fines the high-speed physical medium attachment (PMA); — Part de fines the low-speed fault-tolerant physical medium attachment (PMA); — Part de fines the time-triggered communication; — Part de fines the power modes of the high-speed physical medium attachment (PMA); — Part de fines the selective wake-up functionality of the high-speed physical medium attachment (PM A) NO TE ISO 11898 -2 is updated in parallel to the update of this part of ISO 11898 to combine the functions described in ISO 11898-2 , ISO 11898-5 and ISO 11898 - (The future edition of ISO 11898-2 will cancel and replace the current ISO 11898-2: 20 03 , ISO 11898 -5: 20 07 and ISO 11898 - 6: 2013) Figure NO TE shows the relations between the OSI reference layers and the parts of the ISO 11898 series ISO 11898-2 refers to the future edition that will cancel and replace the current ISO 11898-2: 20 03 , ISO 11898-5: 20 07 and ISO 11898- 6: 2013 Figure — C AN data link and physical sub-layers relation to the OSI model © ISO 01 – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n vii I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n INTERNATIONAL STANDARD ISO 11898-1:2 015(E) Road vehicles — Controller area network (CAN) — Part : Data link layer and physical signalling Scope This part of ISO 11898 speci fies the characteristics of setting up an interchange of digital information between modules implementing the CAN data link layer Controller area network is a serial communication protocol, which s upports dis tributed real-time control and multiplexing for use within road vehicles and other control applications This part of ISO 11898 speci fies the Classical CAN frame format and the newly introduced CAN Flexible Data Rate Frame format The Classical CAN frame format allows bit rates up to Mbit/s and payloads up to byte per frame The Flexible Data Rate frame format allows bit rates higher than Mbit/s and payloads longer than byte per frame This part of ISO 11898 describes the general architecture of CAN in terms of hierarchical layers according to the ISO reference model for open systems interconnection (OSI) according to ISO/IEC 74981 The CAN data link layer is speci fied according to ISO/IEC 8802-2 and ISO/IEC 8802-3 This part of ISO 11898 contains detailed speci fications of the following (see Figure ) : — logical link control sub-layer; — medium access control sub-layer; — physical coding sub-layer There are three implementation options They are the following: — support of the Classical CAN frame format only, not tolerating the Flexible Data Rate frame format; — support of the Classical CAN frame format and tolerating the Flexible Data Rate frame format; — s upport of the C lassical C AN frame format and the F lexible Data Rate frame format The las t option is recommended to be implemented for new designs NOTE Implementations of the first option can communicate with implementations of the third option only as long as the Flexible Data Rate frame format is not used; otherwise, Error Frames are generated There are opportunities to run implementations of the first option also in CAN networks using the Flexible Data Rate frame format, but these are not in the s cop e of this p art of I SO 11 Conformance The data link layer conformance test plan is not in the scope of this part of ISO 11898 For an implementation to be compliant with this part of ISO 11898, the logical link control sub-layer and the medium access control sub-layer shall comply with all mandatory speci fications and values given in this part of ISO 11898 If optional speci fications and values are implemented, they shall comply, too © ISO – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n ISO 11898-1:2 015(E) Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies Information technology — Open Systems Interconnection — Basic Reference Model: The Basic Model — Part I S O/ I E C 74 -1 , I S O/ I E C / I E E E 8 - : 14 , Standard for Ethernet — Part 4 Terms and de initions f For the purpose of this part of ISO 11898, the following terms and de finitions apply 4.1 arbitration phase p h a s e whe re the no m i n a l b i t ti me i s u s e d 4.2 bit stuf ing f frame coding method providing bus state changes required for periodic resynchronization when using a n N R Z b i t re p re s e n tatio n Note to entry: Whenever the transmitting logic encounters a certain number (stuff width) of consecutive bits of equal value in the data, it automatically stuffs a bit of complementary value—a stuff bit—into the outgoing bit s tr e a m Re c e i ve r s d e - s tu ff th e D at a F r a m e s a n d the Re m o te F r a me s , i e th e i n ve r s e p r o c e du r e i s c a r r i e d o u t bus topology of a communication network, where all nodes are reached by passive links which allow tra n s m i s s i o n i n b o th d i re c tio n s 4.4 bus comparator electronic circuit converting physical signals used for transfer across the communication medium back i n to lo g ic a l i n fo r m atio n o r d at a s i g n a l s 4.5 bus driver electronic circuit converting information or data signals into physical signals so that these signals can b e tra n s fe r re d ac ro s s the c o m mu n ic ati o n me d iu m 4.6 bus state one of two complementary logical states: dominant or recessive Note to entry: The dominant state represents the logical 0, and the recessive state represents the logical D u r i n g s i mu l t a n e o u s tr a n s m i s s i o n o f m i n a n t a n d r e c e s s i ve b i t s , th e r e s u l ti n g b u s s t a te i s d o m i n a n t W he n n o tr a n s m i s s i o n i s i n p r o g r e s s , the b u s i s i d l e D u r i n g i d l e ti me , i t i s i n r e c e s s i ve s t ate 4.7 Classical Base Frame Format format for Data Frames or Remote Frames using an 11-bit identi fier, which are transmitted with one single bit rate and up to and including data bytes 4.8 Classical Extended Frame Format format for Data Frames or Remote Frames using a 29-bit identi fier, which are transmitted with one single bit rate and up to and including data bytes I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © I S O – Al l ri gh ts re s e rve d ISO 11898-1:2 015(E) The maximum tolerance df < df < df < df < df of fosc shall meet the following conditions: SJW( N ) × 10 × bit time ( N ) N N− min[Phas e _S eg1( × [1 × b it time( (3) ) , Phas e_S eg2( ) Phas e_S e g2( N N )] (4) )] SJW( D ) × 10 × bit time( D ) (5 ) min[Phase_Seg1( N ), Phase_Seg2( N )] m( D ) + × bit time( N ) × [6 × bit time( D ) − Phase_S e g2( D )] × m( N ) (6) m( N ) SJW( D ) − max , −1 m (D) df < (N) m + Phase_Seg2( D ) + × bit time( D ) × [ × bit time( N ) − Phase_Seg2( N ) ] × m( D ) (7 ) where N) indicates the values for the arbitration phase; D indicates the values for the data phase ( ( ) The conditions given in Formulas (3) and (4) shall be met for Classical Frames; all conditions of Formulas (3) to (7 ) shall be met for FD Frames It is to be considered that SJW may not be larger than the smaller of the phase buffer segments and that the propagation time segment limits that part of the bit time that may be used for the phase buffer segments 11.3 Transmitter delay compensation CAN nodes are connected to the CAN network via an electrical circuit, the transceiver, that unavoidably imposes a time delay between the point in time when a bit is transmitted at the protocol controller’s output signal and the point in time when the same bit signal appears at the protocol controller’s input signal Without transmitter delay compensation, the bit rate in the data-phase of FD Frames is limited by the fact that the transmitter detects a bit error if it cannot receive its own transmitted bit latest at the sample point of that bit FD enabled implementations shall support a transmitter delay compensation mechanism, to be used in applications where the length of the bit time in the data phase is shorter than the propagation delay from the PCS to PM A output message (see 11.4.2 1) to the PM A to PCS input message (see 11 1) as speci fied in other parts of ISO 11898 This mechanism shall only be used by transmitters in the data phase of FD Frames, when BRS is recessive It shall be programmable whether the mechanism is used at m (D) shall be one or two The implementation shall be able to compensate transmitter delays of at least two data bit times all When this mechanism is used, the value of the prescaler for the data time quantum NOTE The PCS to PM A output message corresponds to a transceiver’s bus driver input pin RxD, the PM A to PCS input message corresponds to a transceiver’s bus comparator output pin TxD The transmitter delay compensation mechanism de fines a secondary sample point SSP When it is used, the transmitter shall ignore bit errors detected at the sample point The received bit value shall be compared, at the SSP, with the (delayed) transmitted bit value If a bit error is detected at the SSP, the transmitter shall react to this bit error at the subsequent following sample point Bit error detection shall be disabled for those bits at the end of the data phase where the SSPs of the bits would be in the following arbitration phase 52 I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © ISO 01 – All rights reserved ISO 11898-1:2 015(E) Figure — Position of the secondary sample point The position of the SSP shall be speci fied by its distance from the start of the bit time The figuration range for this S SP pos ition shall be at leas t to 63 minimum time quanta The SSP position shall either be set to a fixed value or it shall be set to a value derived from a measurement of the actual transmitter delay The measurement of the transmitter delay shall be done in each transmitted frame at the reces sive to dominant edge from the FDF bit to the res bit Application of the meas ured value for the SSP pos ition will be done at the data phase of the s ame frame A counter shall be s tarted when the transmitter s tarts to transmit the dominant res bit at the transmit output T he counter shall be incremented by one each minimum time quantum until the dominant signal is detected at the receive input; then the counter shall be stopped The counter value is the measured transmitter delay time When the SSP position is derived from the delay measurement, the position shall be the sum of the measured transmitter delay value and a figurable SSP offset shows the relation between the transmitter delay and the SSP position In that example, the transmitter delay is almost two data bit times long Therefore the SSP is placed in the range from the transmitter delay up to three data bit times after the start of the bit; The example bit s tream [A, B , … K] in Figure at a point where the input signal is expected to have s tabilized I n this case, the bits from the received bit stream shall be compared to the bits from the transmitted bit stream that are delayed by two data bit times: At SSP , the received bit A is compared to the delayed transmitted bit A and so on A R Optionally, if SSP position value is an odd number and the value of the prescaler for the data time quantum is 2, then SSP position may be determined by dividing the SSP position value by and rounding down the result Figure shows the end of the data phase with transmitter delay compensation The SSP sequence stops at the transmitter’s sample point of the (first) CRC Delimiter bit, where the data phase ends The actual NO TE received bit value is ignored at the s ample p oint, the S SP sequence is s topp ed I n that example, the las t C RC sequence bit before the CRC Delimiter is locally disturbed (received bit E R is seen reces s ive, but was trans mitted dominant) T he trans mitter tolerates a s econd reces s ive C RC D elimiter bit b efore it sees the dominant AC K T here would be an EF instead of the ACK if the disturbance of bit E were not locally limited © ISO – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n 53 ISO 11898-1:2 015(E) Figure 25 — End of transmitter delay compensation phase CAN implementations may choose to continue the SSP sequence beyond the limit of the data phase, c he c ki n g fo r l o c a l e r ro r s at the tra n s m i t ti n g no de a s s ho w n i n F i g u re Figure 26 — Optional continuation of SSP sequence 11.4 AUI speci ication f 11.4.1 General The attachment unit interface is the interface between the PCS that is speci fied in this part of ISO 11898 and the PMA that is speci fied in other parts of ISO 11898 or other ISO standards (e.g ISO 11992-1) 54 I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © I S O – Al l ri gh ts re s e rve d ISO 11898-1:2 015(E) 11.4.2 PCS to PMA messages 11.4.2 Output message The PCS shall send an output message to the PMA sub-layer whenever it receives an Output_Unit from the MAC sub-layer The output message causes the PMA to send a dominant or recessive bit 11.4.2 Bus_off message The PCS shall send a bus_off message to the PMA sub-layer whenever it receives a bus_off_request from the supervisor (see 12 1) 11.4.2 Bus_off_release message The PCS shall send a bus_off_release message to the PMA sub-layer whenever it receives a bus_off_ release_request from the supervisor (see 12 1) 11.4.2 FD_Transmit message The PCS shall send an FD_Transmit message to the PMA sub-layer whenever it receives an FD_Transmit from the MAC sub-layer This message is optional for FD enabled implementations 11.4.2 FD_Receive message The PCS shall send an FD_Receive message to the PMA sub-layer whenever it receives an FD_Receive from the MAC sub-layer This message is optional for FD-enabled implementations 11.4.3 PMA to PCS message 11.4.3 Input message The PMA sub-layer shall send an input message to the PCS whenever the PMA has received a bit from the medium The input signal indicates to the PCS the arrival of a dominant or recessive bit 12 Description of supervisor FCE 12.1 Fault con inement f 12 1.1 Obj ectives The objective of fault finement is to preserve a high availability of the data transmission network even in the presence of a defective node Therefore, the fault finement strategies shall prove reliable on the following instances: a) distinction between temporary errors and permanent failures; b) localization and switching-off of faulty nodes 12 1.2 Strategies All nodes shall include a transmit error counter and a receive error counter The transmit error counter shall register the number of errors during the transmission, and the receive error counter shall register the errors during the reception of frames When frames are sent or received correctly, the counters shall be decremented When frames are sent or received with errors, the counters shall be incremented more than they are decremented in the absence of errors The ratio in which the counters are incremented/decremented depends on the © ISO 01 – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n 55 ISO 11898-1:2 015(E) acceptable ratio of invalid/valid frames on the bus At any time the levels of the error counters re flect the relative frequency of previous errors D ep end i ng on p re de te r m i ne d c o u nte r va lue s , the b e h av io u r of no de s in re s p e c t to e r ro r s shal l be modi fied I.e this shall range from a prohibition of sending error flags to cancel frames, up to switchingo ff o f no de s wh i ch o fte n s e n d i nva l id fra me s 12.1.3 Fault con inement interface speci ication f f 12 1.3 Description Fault finement interface shall be as given in F i g u re Figure 27 — Fault con inement interface f 56 I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © I S O – Al l ri gh ts re s e rve d ISO 11898-1:2 015(E) 12 1.3 LLC sub-layer/FCE interface The messages interchanged between the FCE and the LLC sub-layer shall be as given in Table and Table 10 Table — LLC-to-FCE message Message Normal _Mode _Request Description Resets FCE to initial s tate (the values of the transmit error counter and the receive error counter are set to zero when the FCE passes into its initial s tate) Table 10 — FCE-to-LCC message Message Description Normal _Mode _Response Response to the Normal _Mode _Request Bus _Off Indicates that the node is in the bus-off state 12 1.3 MAC sub-layer/FCE interface The messages exchanges between the FCE and the MAC sub-layer shall be as given in Table 11 and Table 12 Table 11 — M AC-to-FCE messages Messages Transmit/receive Description Indicates the node’s current transfer mode Indicates that the MAC sub-layer has detected an error (bit error, stuff error, Error CRC error, form error, ACK error) Primary_error Error/overload flag Counters _unchanged Signals that the MAC sub-layer has detected a dominant bit after sending an error flag (indicates that the MAC sub-layer has detected a primary error and not an error that is caused by the error flag of another node) Indicates that the MAC sub-layer is sending an error flag or an overload flag Indicates that the FCE counters remain unchanged (due to special cases; see rule c) in 2) Error_delimiter_too_late Indicates that the MAC sub-layer is waiting too long for error delimiter This signal is set each time after a sequence of eight consecutive dominant bits have Successful _transfer been received after sending an error flag Indicates that transmission/reception was successfully completed Error_passive_response Indicates that the node was set into the error passive s tate Error_active response Indicates that the node was set into the error active state again Table 12 — FCE-to-M AC messages Message Description Error_passive_request Reques t to set the node into the error passive state Error_active_reques t Reques t to set the node into the error active s tate 12 1.3 PL/FCE interface The messages exchanged between the FCE and the PL shall be as given in Table 13 and Table 14 © ISO 01 – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n 57 ISO 11898-1:2 015(E) Table 13 — FCE-to-PL messages Message Description Bus _off_reques t Reques t to s witch off the node from the bus Bus _off_release_reques t Reques t to set the node into the normal transmit/receive node Table 14 — PL-to-FCE messages Message Description Bus _off_response Response to bus _off_reques t Bus _off_release_response Response to bus _off_release _request 12.1.4 Rules of fault con inement f 12 1.4.1 Description With respect to fault finement, a node may be in one of the three states, depending on the error counter levels (see 6.13 and 6.15 ) : — error-active; — error-passive; — bus-off 12 1.4.2 Error counting The error counters shall be modi fied according to the following rules (more than one rule may apply during a given frame transfer) a) When a receiver detects an error, the receive error counter shall be incremented by 1, except when the detected error was a bit error during the sending of an active error flag or an overload flag b) When a receiver detects a dominant bit as the first bit after sending an error flag, the receive error counter shall be incremented by c) When a transmitter sends an error flag, the transmit error counter shall be incremented by E xception 1: If the transmitter is error-passive and detects an ACK error because of not detecting a dominant ACK and does not detect a dominant bit while sending its passive error flag E xception 2: If the transmitter sends an error flag because a stuff error occurred during arbitration, whereby the stuff bit should have been recessive, and has been sent recessive but is monitored to be dominant In exception and in exception , the transmit error counter remains unchanged d) If a transmitter detects a bit error while sending an active error flag or an overload flag, the transmit error counter shall be incremented by e) If a receiver detects a bit error while sending an active error flag or an overload flag, the receive error counter shall be incremented by f) Any node shall tolerate up to consecutive dominant bits after sending an active error flag, passive error flag, or overload flag After detecting 14 consecutive dominant bits (in case of an active error flag or an overload flag) or after detecting consecutive dominant bits following a passive error flag, 58 I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © ISO 01 – All rights reserved ISO 11898-1:2 015(E) and after each sequence of additional consecutive dominant bits, every transmitter shall increment its transmit error counter by and every receiver shall increment its receive counter by g) h) After the successful transmission of a frame (getting ACK and no error has been detected until EOF is finished), the transmit error counter shall be decremented by unless it was already After the successful reception of a frame (reception without error up to the ACK slot and the successful sending of the ACK bit), the receive error counter shall be decremented by 1, if it was between and 127 If the receive error counter was 0, it shall stay at 0, and if it was greater than 127, then it shall be set to a value between 119 and 127 12 1.4.3 Transition between error-active and error-passive states If the transmit error counter or the receive error counter of a node exceeds 127 (carry condition in case of a 7-bit receive error counter) then the supervisor shall request the MAC sub-layer to set the corresponding node into the error-passive state An error condition causing a node to become error-passive shall cause the node to send an active error f lag An error-passive node shall become error-active again when both the transmit error counter and the receive error counter are less than or equal to 127 (see Figure 8) When the receive error counter of a node exceeds the error-passive limit of 127, further increments of this receive error counter shall be limited by the width of the counter At the next successful reception of a frame (transition to error-active) , the receive error counter shall be set to a value below the errorpassive limit [see error counting rule h) in 12 2] 12 1.4.4 Bus-off management If the transmit error counter of a node is greater than 255 (carry condition in case of a 8-bit transmit error counter) then the supervisor shall request the PL to set the node into the bus-off state A node which is in the bus-off state shall have no in fluence on the bus It shall not send any frames nor acknowledge DFs or RFs Whether or not such a node accepts DFs from the bus depends on the implementation Upon a restart request, a node which is in the bus- off state shall be integrating to the C AN communication (see 10.9.4 ) and may become error-active (no longer bus-off) with its error counters both set to zero after having monitored 12 occurrences of the idle condition (see 8) on the bus (see Figure 8) © ISO 01 – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n 59 ISO 11898-1:2 015(E) Figure 28 — Node status transition diagram 12 1.5 Network start-up If during network start-up only one node is online and if this node transmits some frame, it will not get an AC K I n this case, it shall detect an error and repeat the frame According to rule c) in , exception 1, it may become error-passive but shall not go bus-off A node that had been s witched off and is s witched on again shall — synchronize with already available nodes to integrate into the bus communication (see 9) before starting to transmit Synchronization is achieved when 11 recessive bits that are equivalent to: AC K delimiter + EOF + I ntermission or Error/overload delimiter + Intermission have been detected; — wait for other nodes if there is no other node available at the moment without becoming bus- off 12 Bus failure management During normal operation, several bus failures may occur that in fluence the bus operation These failures and the res ulting behaviour of the network shall be in accordance with the used PM A 60 I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © ISO – All rights reserved ISO 11898-1:2 015(E) Annex A (informative) Additional Information A.1 Differences between Classical Frames and FD Frames There are three implementation options for the support of frame formats: a) support for the Classical frame format only, not tolerating the Flexible Data Rate frame format (Classical CAN); b) support for the C lassical frame format and tolerating the Flexible Data Rate frame format (C AN c) support for the Classical frame format and for the Flexible Data Rate frame format (C AN FD enabled) FD tolerant); Option c) is recommended to be implemented for new designs The difference between implementation options a) and b) is the protocol exception event that causes the FD tolerant implementation to enter the bus integration state when a recessive FDF bit is detected That is described in 10.9 The differences between implementation options a) and c) concern the frame formats, CRC mechanisms, acknowledgement and the transmitter delay compensation They are referenced in the following clauses and subclauses: Scope C AN-FD added to the Scope Terms and de finitions 4.1 arbitration phase 4.11 data bit rate 4.1 data bit time 4.14 data phase 4.17 FD enabled 4.18 FD Base Frame Format 4.19 FD E xtended Frame Format 20 FD Frame 21 FD Intolerant 22 FD Tolerant 4.41 Protocol exception event Symbols and abbreviated terms BRS Bit Rate Switch © ISO 01 – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n 61 ISO 11898-1:2 015(E) ESI E r ro r S tate I nd ic ato r FD F le x i b le D at a Rate FDF F D Fo r m at I n d ic ato r FBFF F D B a s e F r a me Fo r m at FEFF F D E x te n de d F r a me Fo r m at re s re s e r ve d b i t i n F D F r a me s RR S Re mo te Re que s t S u b s ti tu tio n Secondary Sample Point SSP Transmitter Delay Compensation TDC 6.8 E r ro r de te c ti o n 17-bit CRC for FD Frames with up to 16 data- field bytes, 21-bit CRC for FD Frames with 20 to 64 data- field bytes Fixed bit stuffing and stuff count in the CRC field of FD Frames Types of connectionless-mode transmission services Four types of frames have been increased to six due to the addition of: L L C D ata F me i n F D B a s e F r a me fo r m at, a nd L L C D ata F me i n F D E x te nde d F r a me fo r m at Format field The following have been added to support the CAN-FD functionality: F B F F F D B a s e F me Fo r m at, a nd F E F F F D E x te nde d F me Fo r m at 4 DLC field DLC has been extended to support the CAN-FD functionality Data field Data field has been extended to support the CAN-FD functionality 10 S tr uc tu re o f M AC fra me s The following have been added to support the CAN-FD functionality: M AC D ata F me i n F D B a s e F me fo r m at, M AC D ata F me i n F D E x te n de d F me fo r m at 10 10 10 62 Arbitration field Control field CRC field ACK field I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © I S O – Al l ri gh ts re s e rve d ISO 11898-1:2 015(E) 10 O rder of bit trans mission Four figures describing FD Frames: Figure , Figure 14, Figure 16 , and Figure 17 10 P rotocol exception event 10 E rror signalling Error signalling when leaving data phase of FD Frame 11 Con figuration of the bit time parameters Con figuration values for data bit time 11 Tolerance range of the oscillator frequencies T hree formulas for FD Frames 11 Transmitter delay compensation Exclusively used for FD Frames Table A.1 — Compatibility between implementations Function Type of implementation C las s ical C AN C AN FD tolerant C AN FD enabled or other when dis a- when dis abling of bling of F lexible D ata C las s ical frame Rate frame format format s upp orted and figured (see s upp orted and con- figured Reception and trans- C AN FD enabled Supp orted 10 9.10) Supp orted Supp orted No recep tion, no mis s ion of C las s ical trans mis s ion E rror Frames Frames wil l b e sent when C las s ical frames pres ent, unles s no de in E rror Pas s ive s tate or generally unable to trans mit Reception and No recep tion, no No recep tion, no trans mis s ion of FD trans mis s ion E rror trans mis s ion, no Frames Frames wi ll b e s ent E rror Frames wi ll b e when FD frames s ent when FD frames present, unles s no de present Supp orted Supp orted in E rror Pas s ive state or generally unable to trans mit © ISO – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n 63 ISO 11898-1:2 015(E) A.2 Non-mandatory implementation features The non-mandatory features speci fied in the standard are listed in Tab le A Table A.2 — Optional features No Optional feature F D fr a m e fo r m a t D i s ab l i n g o f fr a me fo r m a ts L i m i te d L L C fr a m e s No transmission of frames including padding bytes L L C Ab o r t i n te r fac e E S I a n d B R S b i t va l u e s Method to provide MAC data consistency T i m e a n d ti m e tr i g ge r i n g T i m e s t a mp i n g 10 B u s m o n i to r i n g m o de 11 H a nd le 12 Re s tr i c te d o p e r a ti o n 13 S e p a r a te p r e s c a l e r s fo r n o m i n a l b i ts a n d fo r d a t a b i t s 14 D i s ab l i n g o f au to m a tic r e tr a n s m i s s i o n 15 M a x i mu m nu m b e r o f r e tr a n s m i s s i o n s 16 D i s a b l i n g o f p r o to c o l e xc e p ti o n e ve n t o n r e s b i t de te c te d r e c e s s i ve 17 P C S _ S t atu s 18 Edge filtering during the bus integration state 19 T i me r e s o l u ti o n fo r S S P p l ac e me n t 20 F D _T/ R me s s a ge A.3 Described in C l au s e 1 8.5 8.5 , x, 10 10 4, , 10 9.4 , 14 4, x, 4.1 10 10 , 10 11 1 , 11 43 , , , 10 4 11 , 11 4, 11 , 1 11 11 4, 11 Implementation hints This part of ISO 11898 speci fies the CAN communication on the CAN network; it does not specify the i n te r face b e t we e n a n i mp le me nt atio n o f the C A N p ro to co l a nd a ho s t co n tro l le r T h i s a l lo ws i nte g ratio n o f C A N i mp le me nt atio n s i nto s i mp l e s e n s o r o r ac to r no de s , a s we l l a s i n to µC s o r a s s e p a rate I C s If the implementation allows to change the figuration of a node by software, the figuration data (e.g bit time figuration, operating mode) needs to be locked against changes while the CAN co m mu n i c ati o n i s o n go i n g 64 I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n © I S O – Al l ri gh ts re s e rve d ISO 11898-1:2 015(E) Bibliography [1] ISO 76 7-3 , Road vehicles — Electrical disturbances from conduction and coupling — Part 3: Electrical tran sient tran smission by capacitive and inductive coupling via lines other than supply lines [2 ] I S O 19 -1 , Road vehicles — Interch an ge of digital inform ation on electrical n ection s between towin g an d towed vehicles — Part : Physical an d data-link layers [3 ] I S O/ I E C 8 -2 , In form ation tech n ology — Telecom munication s an d inform ation exch an ge between systems — Local and metropolitan area networks — Specific requirements — Part 2: Logical lin k trol [4] I S O/ I E C 8 -2 : 19 8/C o r : 0 © I S O – Al l ri gh ts re s e rve d I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n 65 ISO 11898-1:2 015(E) ICS 43.040.15 Price based on 65 pages © ISO 2015 – All rights reserved I n tern ati o n al Org an i z ati o n fo r S tan d ard i z ati o n