ISO 11898-1:2015

INTERNATIONAL ISO
STANDARD 11898-1
Second edition
2015-12-15
Road vehicles — Controller area
network (CAN) —
Part 1:
Data link layer and physical signalling
Véhicules routiers — Gestionnaire de réseau de communication
(CAN) —
Partie 1: Couche liaison de données et signalisation physique
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .vi
Introduction .vii
1 Scope . 1
2 Conformance . 1
3 Normative references . 2
4 Terms and definitions . 2
5 Symbols and abbreviated terms . 5
6 Basic concepts of CAN . 7
6.1 CAN properties . 7
6.2 Frames . 8
6.3 Bus access method . 8
6.4 Information routing . 8
6.5 Network flexibility . 8
6.6 Data consistency . 8
6.7 Remote data request . 8
6.8 Error detection . 9
6.9 Error signalling and recovery time . 9
6.10 ACK . 9
6.11 Automatic retransmission . 9
6.12 Fault confinement. 9
6.13 Error-active . 9
6.14 Error-passive . 9
6.15 Bus-off .10
7 Layered architecture of CAN .10
7.1 Reference to OSI model .10
7.2 Protocol specification .11
7.3 Format description of services .11
7.3.1 Format description of service primitives .11
7.3.2 Types of service primitives .12
7.4 LLC interface .12
8 Description of LLC sub-layer .12
8.1 General .12
8.2 Services of LLC sub-layer .13
8.2.1 Types of connectionless-mode transmission services .13
8.2.2 Service primitive specification .13
8.3 Functions of LLC sub-layer .18
8.3.1 General.18
8.3.2 Frame acceptance filtering .18
8.3.3 Overload notification .18
8.3.4 Recovery management .19
8.4 Structure of LLC frames .19
8.4.1 General.19
8.4.2 Specification of LLC DF .19
8.4.3 Specification of LLC RF .20
8.5 Limited LLC frames .21
9 Interface between LLC and MAC .21
9.1 Services .21
9.2 Time and time triggering .21
9.2.1 Description . . .21
9.2.2 Time base .21
9.2.3 Time reference point .21
9.2.4 Event generation .22
9.3 Disabling automatic retransmission .22
9.3.1 Retransmission of frames.22
9.4 Message time stamping .22
10 Description of MAC sub-layer .22
10.1 General .22
10.2 Services of MAC sub-layer .22
10.2.1 Service description .22
10.2.2 Service primitives specification .23
10.3 Functional model of MAC sub-layer architecture .27
10.3.1 Capability .27
10.3.2 Frame transmission . .27
10.3.3 Frame reception .28
10.4 Structure of MAC frames.29
10.4.1 Description . . .29
10.4.2 Specification of MAC DF .29
10.4.3 Specification of MAC RF .34
10.4.4 Specification of EF .34
10.4.5 Specification of OF .35
10.4.6 Specification of inter-frame space .36
10.5 Frame coding .37
10.6 Frame acknowledgement .37
10.7 Frame validation .37
10.8 Order of bit transmission .38
10.9 Medium access method .39
10.9.1 General.39
10.9.2 Multi-master .39
10.9.3 Bus access .40
10.9.4 Bus integration state .40
10.9.5 Protocol exception event.40
10.9.6 Transmission of MAC frames .40
10.9.7 Content-based arbitration .40
10.9.8 Frame priority .41
10.9.9 Collision resolution .41
10.9.10 Disabling of frame formats .41
10.10 MAC data consistency .41
10.11 Error detection .41
10.12 Error signalling .42
10.13 Overload signalling .43
10.14 Bus monitoring .44
10.15 Restricted operation . .44
11 PL specification .44
11.1 General and functional modelling .44
11.2 Services of PL .44
11.2.1 Description . . .44
11.2.2 PCS_Data.Request .45
11.2.3 PCS_Data.Indicate .45
11.2.4 PCS_Status.Transmitter .45
11.2.5 PCS_Status.Receiver.45
11.3 PCS specification.45
11.3.1 Bit encoding/decoding .45
11.3.2 Synchronization .50
11.3.3 Transmitter delay compensation.52
11.4 AUI specification .54
11.4.1 General.54
11.4.2 PCS to PMA messages .55
11.4.3 PMA to PCS message .55
iv © ISO 2015 – All rights reserved

12 Description of supervisor FCE .55
12.1 Fault confinement.55
12.1.1 Objectives .55
12.1.2 Strategies .55
12.1.3 Fault confinement interface specification .56
12.1.4 Rules of fault confinement .58
12.1.5 Network start-up .60
12.2 Bus failure management .60
Annex A (informative) Additional Information .61
Bibliography .65
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 1. 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 2 (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 identified 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 specific 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 (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 22, Road vehicles, Subcommittee SC 31, Data
communication.
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 Road vehicles — Controller area
network (CAN):
— Part 1: Data link layer and physical signalling
1)
— Part 2: High-speed medium access unit
— Part 3: Low-speed, fault-tolerant, medium-dependent interface
— Part 4: Time-triggered communication
1)
— 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) Parts 2, 5, and 6 are being revised. They will be merged under a new edition of Part 2.
vi © ISO 2015 – All rights reserved

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 1 defines 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 2 defines the high-speed physical medium attachment (PMA);
— Part 3 defines the low-speed fault-tolerant physical medium attachment (PMA);
— Part 4 defines the time-triggered communication;
— Part 5 defines the power modes of the high-speed physical medium attachment (PMA);
— Part 6 defines the selective wake-up functionality of the high-speed physical medium attachment
(PMA).
NOTE 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 11898-6. (The future edition of ISO 11898-2 will cancel and
replace the current ISO 11898-2:2003, ISO 11898-5:2007 and ISO 11898-6:2013)
Figure 1 shows the relations between the OSI reference layers and the parts of the ISO 11898 series.
NOTE ISO 11898-2 refers to the future edition that will cancel and replace the current ISO 11898-2:2003,
ISO 11898-5:2007 and ISO 11898-6:2013.
Figure 1 — CAN data link and physical sub-layers relation to the OSI model
INTERNATIONAL STANDARD ISO 11898-1:2015(E)
Road vehicles — Controller area network (CAN) —
Part 1:
Data link layer and physical signalling
1 Scope
This part of ISO 11898 specifies 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 supports distributed real-time control and multiplexing for use within
road vehicles and other control applications.
This part of ISO 11898 specifies 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 1 Mbit/s and payloads
up to 8 byte per frame. The Flexible Data Rate frame format allows bit rates higher than 1 Mbit/s and
payloads longer than 8 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 7498-
1. The CAN data link layer is specified according to ISO/IEC 8802-2 and ISO/IEC 8802-3.
This part of ISO 11898 contains detailed specifications of the following (see Figure 2):
— 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;
— support of the Classical CAN frame format and the Flexible Data Rate frame format.
The last 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 scope of this part of ISO 11898.
2 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 specifications and values given in
this part of ISO 11898. If optional specifications and values are implemented, they shall comply, too.
3 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.
ISO/IEC 7498-1, Information technology — Open Systems Interconnection — Basic Reference Model: The
Basic Model — Part 1
ISO/IEC/IEEE 8802-3:2014, Standard for Ethernet — Part 3
4 Terms and definitions
For the purpose of this part of ISO 11898, the following terms and definitions apply.
4.1
arbitration phase
phase where the nominal bit time is used
4.2
bit stuffing
frame coding method providing bus state changes required for periodic resynchronization when using
an NRZ bit representation
Note 1 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
stream. Receivers de-stuff the Data Frames and the Remote Frames, i.e. the inverse procedure is carried out.
4.3
bus
topology of a communication network, where all nodes are reached by passive links which allow
transmission in both directions
4.4
bus comparator
electronic circuit converting physical signals used for transfer across the communication medium back
into logical information or data signals
4.5
bus driver
electronic circuit converting information or data signals into physical signals so that these signals can
be transferred across the communication medium
4.6
bus state
one of two complementary logical states: dominant or recessive
Note 1 to entry: The dominant state represents the logical 0, and the recessive state represents the logical 1.
During simultaneous transmission of dominant and recessive bits, the resulting bus state is dominant. When no
transmission is in progress, the bus is idle. During idle time, it is in recessive state
4.7
Classical Base Frame Format
format for Data Frames or Remote Frames using an 11-bit identifier, which are transmitted with one
single bit rate and up to and including 8 data bytes
4.8
Classical Extended Frame Format
format for Data Frames or Remote Frames using a 29-bit identifier, which are transmitted with one
single bit rate and up to and including 8 data bytes
2 © ISO 2015 – All rights reserved

4.9
Classical Frame
Data Frame or Remote Frame using the Classical Base Frame Format or the Classical Extended Frame
Format
4.10
content-based arbitration
CSMA arbitration procedure resolving bus-contention when multiple nodes simultaneously access the bus
4.11
data bit rate
number of bits per time during data phase, independent of bit encoding/decoding
4.12
data bit time
duration of one bit in data phase
4.13
Data Frame
frame containing user data (e.g. one or more signals or one or more suspect parameters of one or more
process data)
4.14
data phase
phase where the data bit time is used
4.15
edge
difference in bus-states between two consecutive time quanta
4.16
Error Frame
frame indicating the detection of an error condition
4.17
FD enabled
able to receive and to transmit FD Frames, as well as Classical Frames
4.18
FD Base Frame Format
format for Data Frames using an 11-bit identifier, which are transmitted with a flexible bit rate and up
to and including 64 data bytes
4.19
FD Extended Frame Format
format for Data Frames using a 29-bit identifier, which are transmitted with a flexible bit rate and up to
and including 64 data bytes
4.20
FD Frame
Data Frame using the FD Base Frame Format or FD Extended Frame Format
4.21
FD intolerant
only able to receive or to transmit Classical Frames, disturbing FD Frames
4.22
FD tolerant
not able to receive or to transmit FD Frames but not disturbing them
4.23
frame
Protocol Data Unit of the data link layer specifying the arrangement and meaning of bits or bit fields in
the sequence of transfer across the transmission medium
4.24
handle
hardware object label of one or multiple LLC frames (LPDU)
4.25
higher-layer protocol
protocol above the Data Link Layer protocol according to the Open System Interconnection model
[SOURCE: ISO/IEC 7498-1]
4.26
identifier
does not indicate the destination of the frame but reflects the priority of a particular frame and denotes
the meaning of the data
4.27
idle
state of the network, when there is recessive state after the completion of a frame
4.28
idle condition
detection of a sequence of eleven consecutive sampled recessive bits
4.29
integrating
status of a node waiting on an idle condition after it has started the protocol operation during bus-off
recovery or after a protocol exception event
4.30
minimum time quantum
smallest time quantum that can be configured for the specific implementation
4.31
multicast
addressing where a single frame is addressed to a group of nodes simultaneously
Note 1 to entry: Broadcast is a special case of multicast, whereby a single frame is addressed to all nodes
simultaneously.
4.32
multi master
network with several nodes where every node is able to temporarily control the action of other nodes
4.33
node
assembly, linked to a communication network, capable of communicating across the network according
to a communication protocol specification
Note 1 to entry: A CAN node is a node communicating across a CAN network.
4.34
node clock
time base to coordinate the bit-time-related state machines in CAN implementations
4.35
nominal bit rate
number of bits per time during arbitration phase, independent of the bit encoding/decoding
4 © ISO 2015 – All rights reserved

4.36
nominal bit time
duration of one bit in arbitration phase
4.37
Non-Return-to-Zero
method of representing binary signals, i.e. within one and the same bit time, the signal level does not
change, where a stream of bits having the same logical value provides no edges
4.38
Overload Frame
frame indicating an overload condition
4.39
priority
attribute to a frame controlling its ranking during the arbitration
Note 1 to entry: A high priority increases the probability that a frame wins the arbitration process.
4.40
protocol
formal set of conventions or rules for the exchange of information between nodes, including the
specification of frame administration, frame transfer and PL
4.41
protocol exception event
exception from the formal set of conventions or rules to be able to tolerate future new frame formats
4.42
receiver
any node that is not transmitter or integrating when the bus is not idle
4.43
Remote Frame
frame that requests the transmission of a dedicated Data Frame
4.44
stuff bit count
number of stuff bits in a frame before the CRC field, not including fixed stuff bits
4.45
time-triggered communication
option where a frame can be transmitted in a defined time slot, which also provides a network-wide
synchronization of clocks, as well as disabling of the automatic retransmission of frames, so that dedicated
data and remote frames avoid collisions with data and remote frames transmitted by other nodes
4.46
transceiver
electronic circuit that connects a CAN node to a CAN network, consisting of a bus comparator and a bus
driver
4.47
transmitter
node originating a data frame or remote frame, and stays transmitter until the bus is idle again or until
the node loses arbitration
5 Symbols and abbreviated terms
ACK Acknowledgement
AUI Attachment Unit Interface
BCH Bose-Chaudhuri-Hocquenghem
BRS Bit Rate Switch
CAN Controller area network
CBFF Classical Base Frame Format
CEFF Classical Extended Frame Format
CRC Cyclic Redundancy Check
CSMA Carrier Sense Multiple Access
DF Data Frame
DLC Data Length Code
DLL Data Link Layer
EF Error Frame
EOF End Of Frame
ESI Error State Indicator
FBFF FD Base Frame Format
FCE Fault Confinement Entity
FD Flexible Data Rate
FDF FD Format indicator
FEFF FD Extended Frame Format
HLP Higher-Layer Protocols
IDE IDentifier Extension
IPT Information Processing Time
LAN Local Area Network
LLC Logical Link Control
LME Layer Management Entity
LPDU LLC Protocol Data Unit
LSDU LLC Service Data Unit
MAC Medium Access Control
MAU Medium Attachment Unit
MDI Medium Dependent Interface
MPDU MAC Protocol Data Unit
6 © ISO 2015 – All rights reserved

MSB Most Significant Bit
MSDU MAC Service Data Unit
NRZ Non-Return-to-Zero
OF Overload Frame
OSI Open Systems Interconnection
OVLD Overload
PCI Protocol Control Information
PCS Physical Coding Sub-layer
PDU Protocol Data Unit
PL Physical Layer
PMA Physical Medium Attachment
r0 Reserved bit in Classical Extended Frame Format
res Reserved bit in FD Frames
RF Remote Frame
RRS Remote Request Substitution
RTR Remote Transmission Request
SAP Service Access Point
SDU Service Data Unit
SJW Synchronization Jump Width
SOF Start Of Frame
SP Sample Point
SRR Substitute Remote Request
SSP Secondary Sample Point
TDC Transmitter Delay Compensation
6 Basic concepts of CAN
6.1 CAN properties
CAN has the following properties:
— multi-master priority-based bus access;
— non-destructive content-based arbitration;
— all frame transfer is done as broadcast;
— multicast frame transfer by acceptance filtering;
— remote data request;
— configuration flexibility;
— network-wide data consistency;
— error detection and error signalling;
— automatic retransmission of frames that have lost arbitration, have not been acknowledged, or have
been destroyed by errors during transmission;
— distinction between temporary errors and permanent failures of nodes and autonomous switching-
off of defective nodes.
6.2 Frames
Information on the bus is sent in fixed format frames of different but limited length. When the bus is
idle, any connected node is allowed to start the transmission of a DF or RF. The bus is idle when no
frames are transmitted. Additionally, any connected node may start the indication of error and overload
information by means of dedicated frames (EF and OF, respectively).
6.3 Bus access method
If two or more nodes start to transmit DFs or RFs at the same time, the bus access conflict is resolved
by content-based arbitration using the identifier. The mechanism of arbitration ensures that neither
information nor time is lost. The transmitter with the DF or RF of the highest priority gains the bus
access. A DF with the same ID as an RF wins bus arbitration.
6.4 Information routing
A node does not make use of any information about the network configuration (e.g. node address).
Instead, receivers accept or do not accept information based upon a process called frame acceptance
filtering, which decides whether the received information is relevant or not. There is no need for
receivers to know the transmitter of the information and vice versa.
6.5 Network flexibility
Nodes can be added to the CAN network without requiring any change in the software or hardware of
any node, if the added node is not the transmitter of any DF and if the added node does not require any
additional transmitted data.
6.6 Data consistency
Within a CAN network, a frame can be simultaneously accepted as a valid frame either by all nodes
or by no node. Thus data consistency is a property of the CAN network achieved by the concepts of
broadcast and by error handling.
6.7 Remote data request
By sending an RF, a node requiring data may request another node to send the corresponding DF. The
RF and the corresponding DF are named by the same identifier.
NOTE 1 The node having the message with the requested ID decides whether new data are produced or data
in a transmit buffer will be sent.
NOTE 2 The node having the message with the requested data decides how to respond to an RF with
mismatching DLC.
8 © ISO 2015 – All rights reserved

6.8 Error detection
For detecting errors, the following measures are provided:
— monitoring (transmitters compare the transmitted bit levels with the bit levels detected on the
network);
— 15-bit CRC for Classical Frames, 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;
— stuff bit count check for FD Frames;
— variable bit stuffing with a stuff width of five (except in the CRC field of FD Frames);
— frame format check;
— ACK check.
6.9 Error signalling and recovery time
Corrupted frames are flagged by any transmitting node and any normally operating (error-active)
receiving node. Such frames are aborted and retransmitted according to the implemented recovery
procedure (see 8.3.4). The recovery time from detecting an error until the possible start of the next
frame is typically 17 to 23 nominal bit times (in the case of nodes in error passive mode up to 31 nominal
bit times), if there are no further errors.
6.10 ACK
All receivers check the consistency of the received DFs and RFs, acknowledge a consistent frame,
and flag an inconsistent frame by means of an EF. A transmitting node regards a DF or RF that is not
acknowledged as corrupted.
6.11 Automatic retransmission
Frames that have lost arbitration, frames that have not been acknowledged, and frames that have been
disturbed by errors during transmission are retransmitted automatically until their transmission
has been successfully completed or until their transmission is no longer requested (see 8.3.4 and
10.9.6). Optionally, the automatic retransmission may be disabled (see 9.3). Optionally, the automatic
retransmission may be limited to a certain number of attempts (see 10.9.6).
6.12 Fault confinement
CAN nodes are able to distingui
...