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CAN协议全文英文版,主要为博世发布的标准版,想深耕可以下载
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CAN协议全文英文版,主要为博世发布的标准版,想深耕可以下载
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BOSCH
CAN Specification
Version 2.0
1991, Robert Bosch GmbH, Postfach 30 02 40, D-70442 Stuttgart
BOSCH
ROBERT BOSCH GmbH, Postfach 30 02 40, D-70442 Stuttgart
Sep. 1991
page 1
Recital
The acceptance and introduction of serial communication to more and more
applications has led to requirements that the assignment of message identifiers to
communication functions be standardized for certain applications. These applications
can be realized with CAN more comfortably, if the address range that originally has
been defined by 11 identifier bits is enlarged
Therefore a second message format (’extended format’) is introduced that provides a
larger address range defined by 29 bits. This will relieve the system designer from
compromises with respect to defining well-structured naming schemes. Users of CAN
who do not need the identifier range offered by the extended format, can rely on the
conventional 11 bit identifier range (’standard format’) further on. In this case they can
make use of the CAN implementations that are already available on the market, or of
new controllers that implement both formats.
In order to distinguish standard and extended format the first reserved bit of the CAN
message format, as it is defined in CAN Specification 1.2, is used. This is done in such
a way that the message format in CAN Specification 1.2 is equivalent to the standard
format and therefore is still valid. Furthermore, the extended format has been defined
so that messages in standard format and extended format can coexist within the same
network.
This CAN Specification consists of two parts, with
• Part A describing the CAN message format as it is defined in CAN Specification 1.2;
• Part B describing both standard and extended message formats.
In order to be compatible with this CAN Specification 2.0 it is required that a CAN
implementation be compatible with either Part A or Part B.
Note
CAN implementations that are designed according to part A of this or according to
previous CAN Specifications, and CAN implementations that are designed according to
part B of this specification can communicate with each other as long as it is not made
use of the extended format.
CAN Specification 2.0
PART A
BOSCH
ROBERT BOSCH GmbH, Postfach 30 02 40, D-70442 Stuttgart
Sep. 1991
Part A - page 3
1 INTRODUCTION................................................................................4
2 BASIC CONCEPTS............................................................................5
3 MESSAGE TRANSFER .....................................................................10
3.1 Frame Types ......................................................................................10
3.1.1 DATA FRAME ....................................................................................10
3.1.2 REMOTE FRAME ..............................................................................15
3.1.3 ERROR FRAME.................................................................................16
3.1.4 OVERLOAD FRAME..........................................................................17
3.1.5 INTERFRAME SPACING...................................................................18
3.2 Definition of TRANSMITTER/RECEIVER ..........................................20
4 MESSAGE VALIDATION ...................................................................21
5 CODING.............................................................................................22
6 ERROR HANDLING...........................................................................23
6.1 Error Detection ...................................................................................23
6.2 Error Signalling...................................................................................23
7 FAULT CONFINEMENT.....................................................................24
8 BIT TIMING REQUIREMENTS ..........................................................27
9 INCREASING CAN OSCILLATOR TOLERANCE..............................31
9.1 Protocol Modifications ........................................................................31
Contents
BOSCH
ROBERT BOSCH GmbH, Postfach 30 02 40, D-70442 Stuttgart
Sep. 1991
Part A - page 4
1 INTRODUCTION
The Controller Area Network (CAN) is a serial communications protocol which
efficiently supports distributed realtime control with a very high level of security.
Its domain of application ranges from high speed networks to low cost multiplex wiring.
In automotive electronics, engine control units, sensors, anti-skid-systems, etc. are
connected using CAN with bitrates up to 1 Mbit/s. At the same time it is cost effective to
build into vehicle body electronics, e.g. lamp clusters, electric windows etc. to replace
the wiring harness otherwise required.
The intention of this specification is to achieve compatibility between any two CAN
implementations. Compatibility, however, has different aspects regarding e.g. electrical
features and the interpretation of data to be transferred. To achieve design
transparency and implementation flexibility CAN has been subdivided into different
layers.
• the (CAN-) object layer
• the (CAN-) transfer layer
• the physical layer
The object layer and the transfer layer comprise all services and functions of the data
link layer defined by the ISO/OSI model. The scope of the object layer includes
• finding which messages are to be transmitted
• deciding which messages received by the transfer layer are actually to be used,
• providing an interface to the application layer related hardware.
There is much freedom in defining object handling. The scope of the transfer layer
mainly is the transfer protocol, i.e. controlling the framing, performing arbitration, error
checking, error signalling and fault confinement. Within the transfer layer it is decided
whether the bus is free for starting a new transmission or whether a reception is just
starting. Also some general features of the bit timing are regarded as part of the
transfer layer. It is in the nature of the transfer layer that there is no freedom for
modifications.
The scope of the physical layer is the actual transfer of the bits between the different
nodes with respect to all electrical properties. Within one network the physical layer, of
course, has to be the same for all nodes. There may be, however, much freedom in
selecting a physical layer.
The scope of this specification is to define the transfer layer and the consequences of
the CAN protocol on the surrounding layers.
Introduction
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