ISO 11898:1993

IS0
INTERNATIONAL
STANDARD
First edition
1993-l 1-l 5
Road vehicles - Interchange of digital
information - Controller area network
(CAN) for high-speed communication
V6hicules routiers - khange d ‘informa tion numbrique - Gestionnaire
de rtbeau de communication 9 vitesse B/e&e (CAN)
Reference number
IS0 11898:1993(E)
IS0 11898:1993(E)
Contents
Page
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~.
2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Definitions and
. . . . . . . . . . . . . . . . . . . . . . . . . . . .*.
3.1 Data link layer definitions
. . . . . . . . . . .*.
3.2 Physical layer definitions
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
3.3 List of abbreviations
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Basic concepts of CAN
4.1 Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Bus access method
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Information routing
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4 System flexibility
..,...............................,..............,..................
4.5 Data consistency
,.,.,.,.
4.6 Remote data request
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.7 Error detection
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8 Error signalling and recovery time
..,,.,...,,,.....................,,,.,............................
4.9 Acknowledgement
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.10 Automatic retransmission
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.11 Fault confinement
4.12 ” error-active ” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.13 “error-passive”
,,.*.,.,,.,.,.
4.14 “bus off”
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Layered architecture of CAN
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1 Reference to OSI model
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Protocol specification
. . . . . . . . . . . . .*.
5.3 Format description of services
0 IS0 1993
All rights reserved. No part of this publication may be reproduced or utilized in any form or
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mission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
.......................................................................... 9
5.4 LLC interface
...................................................... 9
6 Description of LLC sublayer
6.1 Services of LLC sublayer . 10
....................................................... 13
6.2 Structure of LLC frames
.................................................... 15
6.3 Functions of LLC sublayer
........................................... 15
7 Interface between LLC and MAC
8 Description of MAC sublayer . 16
8.1 MAC sublayer .
8.2 Services of MAC sublayer . . . . . . . . . . .*.
Functional model of MAC sublayer architecture . 21
8.3
..................................................... 22
8.4 Structure of MAC frames
........................................................................ 27
8.5 Frame coding
8.6 Order of bit transmission .
8.7 Frame validation .
8.8 Medium access method .
8.9 Error detection . 29
.................................................................... 29
8.10 Error signalling
............................................................. 29
8.11 Overload signalling
LLC and MAC sublayer conformance . 30
................................................. 30
10 Description of physical layer
..................................... 30
10.1 Functional model of physical layer
................................................... 31
10.2 Services of physical layer
10.3 Physical Signalling (PLS) sublayer specification .
10.4 PLS-PMA interface specification . 34
10.5 Description of High-Speed Medium Access Unit (HS-MAU) 35
...................................................... 50
11 Description of supervisor
............................................................... 50
11.1 Fault confinement
11.2 Bus failure management .

IS0 11898:1993(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 11898 was prepared by Technical Committee
lSO/TC 22, Road vehicles, Sub-Committee SC 3, Electrical and electronic
equipment.
IS0 11898:1993(E)
INTERNATIONAL STANDARD
- Interchange of digital information -
Road vehicles
Controller area network (CAN) for high-speed
communication
1 Scope
This International Standard specifies characteristics of setting up an interchange of digital information between
Electronic Control Units (ECUs) of road vehicles equipped with the Controller Area Network at transmission rates
above 125 kbit/s up to 1 Mbit/s.
The Controller Area Network (CAN) is a serial communication protocol which supports distributed real-time control
and multiplexing.
This specification of CAN describes the general architecture of CAN in terms of hierarchical layers according to the
IS0 reference model for Open Systems Interconnection (OSI) specified in IS0 7498. The data link layer and
physical layer are specified according to IS0 8802-2 and IS0 8802-3. This International Standard contains detailed
specifications of aspects of CAN belonging to the
a) physical layer;
b) data link layer
- Logical Link Control (LLC) sublayer,
- Medium Access Control (MAC) sublayer.
All other layers of the OSI model do not have counterparts within this specification of CAN protocol but are part
of the user’s level.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part
of IS0 11898. At the time of publication, the editions indicated were valid. All standards are subject to revision,
and parties to agreements based on this part of IS0 11898 are encouraged to investigate the possibility of applying
the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently
valid International Standards.
- Open Systems Interconnection - Basic Reference Model.
I SO 7498: 1984, lnforma tion processing systems
- Electrical disturbance by conduction and coupling - Part 3: Passenger cars and
IS0 7637-3: -l), Road vehicles
light commercial vehicles with nominal 12 V supply voltage and commercial vehicles with 24 V supply voltage -
Electrical transient transmission by capacitive and inductive coupling via lines other than supply lines.
IS0 8802-2:1989, Information processing systems - Local area networks - Part 2: Logical link control.
1) To be published.
IS0 11898:1993(E)
Local and metropolitan area networks - Part 3: Carrier sense
lSO/l EC 8802-3: 1993, Information technology -
multiple access with collision detection (CSMA/CD) access method and physical layer specifications.
3 Definitions and abbreviations
For the purposes of this International Standard, the following definitions apply.
3.1 Data link layer definitions
3.1.1 bit rate: Number of bits per time during transmission, independent of bit representation.
3.1.2 bit stuffing: Technique used in bit-oriented protocols in order
- to achieve data transparency (arbitrary bit patterns may not be interpreted as protocol information), and
- to provide “dominant” to “recessive” edges, and vice versa, which are necessary for correct resynchronization
when using a Non-Return-to-Zero bit representation.
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
destuff the frame, i.e. the inverse procedure is carried out.
3.1.3 bus: Topology of a communication network, where all nodes are reached by passive links which allow
transmission in both directions.
3.1.4 bus value: One of two complementary logical values: “dominant” or “recessive”. The “dominant“ value
During simultaneous transmission of
represents the logical “O“, and the “recessive” represents the logical “1 ‘I.
“dominant” and “recessive” bits, the resulting bus value will be “dominant”.
contention-based arbitration: Carrier Sense Multiple Access (CSMA) arbitration procedure where simul-
3.1.5
taneous access of multiple nodes results in a contention. One frame will survive the contention uncorrupted.
3.1.6 frame: Data link protocol data unit specifying the arrangement and meaning of bits or bit fields in the se-
quence of transfer across the transmission medium.
multicast: Addressing where a single frame is addressed to a group of nodes simultaneously. Broadcast
3.1.7
is a special case of multicast, whereby a single frame is addressed to all nodes simultaneously.
3.1.8 multi-master: System partitioned into several nodes where every node may temporarily control the action
of other nodes.
3.1.9 node: Any assembly, linked to a commun ication line, capable of communicating across the network ac-
Is pecification.
cording to a communication protoco
3.1.1 0 non-return-to-zero: Method of representi ng binary signals . Within one an d the same bit time, the signal
level does not change, i.e. a stream of bits having the same logical value provides no edges.
3.1.11 priority: Attribute to a frame controlling its ranking during arbitration. A high priority increases the proba-
bility that a frame wins the arbitration process.
3.1.12 protocol: Formal set of conventions or rules for the exchange of information between nodes, including
the specification of frame administration, frame transfer and physical layer.
3.1.13 receiver: Device that converts physical signals used for transmission back into logical information or data
signals.
3.1.14 transmitter: Device that converts information or data signals to electrical or optical signals so that these
signals can be transferred across the communication medium.

IS0 11898:1993(E)
3.2 Physical layer definitions
3.2.1 common mode bus voltage range: Boundary voltage levels of VCAN L and VCAN H, for which proper op-
eration is guaranteed if up to the maximum number of ECUs are connected to the bus Iin%.
3.2.2 differential internal capacitance, C diff (of an ECU): Capacitance seen between CAN-L and CAN-H during
the recessive state when the ECU is disconnected from the bus line. (See figure 1.)
3.2.3 differential internal resistance, R diff (of an ECU): Resistance which is seen between CAN-L and CAN-H
during the recessive state when the ECU is disconnected from the bus line. (See figure 1.)
3.2.4 differential voltage, Vdiff: value
V
diff = VCAN-H - VCAN-L
with the voltages VCAN L and VCAN H denoting the voltages of CAN-L and CAN-H relative to ground of each in-
dividual ECU.
3.2.5 internal capacitance, Ci” (of an ECU): Capacitance seen between CAN-L (or CAN-H) and ground during
the recessive state when the ECU is disconnected from the bus line. (See figure 1.)
3.2.6 internal delay time, t Ecu (of an ECU): Sum of all asynchronous delay times occurring on the transmitting
and receiving path relative to the bit timing logic unit of the protocol IC of each individual ECU disconnected from
the bus line.
3.2.7 internal resistance, Ri” (of an ECU): Resistance which is seen between CAN-L (or CAN-H) and ground
during the recessive state when the ECU is disconnected from the bus line. (See figure 1.)
3.2.8
...