29-12-2012, 05:28 PM
CAN Bus
CAN Bus.pdf (Size: 313.78 KB / Downloads: 47)
CAN Introduction
The equivalent of the CAN protocol in human
communication are e.g. the Latin characters.. CAN users
still have to define the language/grammar and the
words/vocabulary to communicate.
CAN provides
a multi-master hierarchy, which allows building intelligent and
redundant systems.
broadcast communication. A sender of information transmits to
all devices on the bus. All receiving devices read the message
and then decide if it is relevant to them.
sophisticated error detecting mechanisms and re-transmission
of faulty messages.
CAN – Protocol
The CAN protocol is an international standard
defined in the ISO 11898. Beside the CAN
protocol itself the conformance test for the
CAN protocol is defined in the ISO 16845,
which guarantees the interchangeability of
the CAN chips.
CAN is based on the “broadcast
communication mechanism”, which is based
on a message-oriented transmission protocol.
Detecting and signaling errors
For error detection the CAN protocol
implements three mechanisms at the
message level:
Cyclic Redundancy Check (CRC)
Frame check
ACK errors
Higher Layer Protocols
To understand the CAN
reference model easier you can
use an analogy. Functionality
provided by CAN is similar to
Latin letters in human
communication. It is the base for
writing a language, but is not
enough to start with efficient
communication.
Implementations of the
CAN protocol
Communication is identical for all implementations of
the CAN protocol. There are differences, however,
with regard to the extent to which the implementation
takes over message transmission from the
microcontrollers which follow it in the circuit.
CAN controller with intermediate buffer.
CAN controller with object storage.
CAN slave controllers for I/O functions.