CAN Physical Layer For Industrial Applications: Public Available Specification
CAN Physical Layer For Industrial Applications: Public Available Specification
CAN Physical Layer For Industrial Applications: Public Available Specification
CiA 102
Version 3.0.0
HISTORY
Date Changes
1994-04-20 Publication of version 2.0 as draft standard
2008-04-10 Publication of version 3.0 as draft standard proposal
Entirely reviewed; references to CiA 301 and CiA 303-1 included.
2010-02-05 Publication of version 3.0 as draft standard (now publicly available)
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CONTENTS
1 Scope ......................................................................................................................... 4
2 Normative references ................................................................................................... 4
3 Definitions and abbreviations........................................................................................ 4
3.1 Definitions .......................................................................................................... 4
3.2 Abbreviations ...................................................................................................... 4
4 Physical signalling ....................................................................................................... 4
4.1 Introduction ........................................................................................................ 4
4.2 Device design ..................................................................................................... 4
4.3 System design .................................................................................................... 5
5 Physical medium attachment ........................................................................................ 5
5.1 Introduction ........................................................................................................ 5
5.2 Device design ..................................................................................................... 5
5.3 System design .................................................................................................... 5
6 Medium dependent interface ........................................................................................ 5
6.1 Introduction ........................................................................................................ 5
6.2 Device design ..................................................................................................... 5
6.3 System design .................................................................................................... 6
1 Scope
This specification describes the Controller Area Network physical layer for general industrial
applications using transmission rates of up to 1 Mbit/s. In addition to the internationally
standardized high-speed transceiver, it specifies a number of transmission rates in order to
achieve a generic compatibility between CAN devices, in particular with CANopen devices.
This specification is suitable for all CAN tools and generic interface devices (e.g. USB/CAN
dongles) to be used for CAN-based industrial networks.
2 Normative references
/CiA301/ CiA 301, CANopen application layer and communication profile
/CiA303-1/ CiA 303-1, CANopen additional specification – Part 1: Cabling and connector
pin assignment
/ISO11898-1/ ISO 11898-1, Road vehicles – Controller area network (CAN) – Part 1: Data
link layer and physical signalling
/ISO11898-2/ ISO 11898-2, Road vehicles – Controller area network (CAN) – Part 2: High-
speed medium access unit
/ISO11898-5/ ISO 11898-5, Road vehicles – Controller area network (CAN) – Part 5: High-
speed medium access unit with low-power mode
3.1.2 T-connector
passive component comprising three connectors
3.2 Abbreviations
4 Physical signalling
4.1 Introduction
The settings of bit-timing parameters for CAN controller chips are not standardized in
/ISO11898-1/.
It is recommended to parameterize the CAN controller chips regarding the sample point as
specified in /CiA301/.
• Interconnected bus line sections – The bus lines consist of a number of sections, which are
interconnected; two options are allowed:
o A T-connector is used to interconnect the bus-line sections and the CAN device.
o The CAN device provides two bus connectors, interconnecting the bus line
The plug connectors shall not provide external power supply for tra nsceiver and optocouplers.
For network length below 40 m it is recommended to use a 124 -Ω resistor to terminate the
bus-lines at both network ends. For other network lengths, general recommendations are
given in /CiA303-1/.
The ground pins of all transceiver chips are interconnected. The parameters of specific
resistance per stub-cable length, total network length, current, and location of the power
supply input should be chosen in a way, that the difference between ground potentials of the
transceiver chips does not exceed 2 V.
NOTE At bus line lengths greater than 40 m, the specific resistance of the bus cable should be lower than the
value given in /ISO11898-2/. The recommendations given in /CiA303-1/ should be considered.
If necessary, galvanic isolation may be applied, in order to reduce the current through the
ground line. In general, it is advantageous to locate the power supply input in the centre of
the bus-lines. It is recommended that the external positive power supply is in the range +7 V <
V+ < +13 V with a maximum of up to 100 mA. Other values should be double -checked with the
used connectors in the entire network.
NOTE If the devices use 24-V or higher voltage power supplies, it is recommended to select appropriate CAN
transceiver chips.
The bus wires may be routed parallel, twisted and/or shielded, depending on the EMC
requirements. If non-terminated stub-cables are used, the maximum length of them should be
considered, for details see /CiA303-1/. The cable stubs should be as short as possible,
especially at higher bit-rates. At 1 Mbit/s, the length of the cable-stubs should not exceed
0,3 m (see /ISO11898-2/); this includes also the device-internal cable stubs.
It is possible to use repeater devices to increase the number of bus nodes, which are
connected to the network system. From the data link layer point of view, it is one logical
network comprising several segments. Repeaters are also used to increase the allowed
distance between the bus nodes.