Rainbow Electronics CAN интерфейс - Manual (Page 10)

BOSCH
ROBERT BOSCH GmbH, Postfach 50, D-7000 Stuttgart 1
Sep. 1991
Part A - page 8
Performance of Error Detection
The error detection mechanisms have the following properties:
- all global errors are detected.
- all local errors at transmitters are detected.
- up to 5 randomly distributed errors in a message are detected.
- burst errors of length less than 15 in a message are detected.
- errors of any odd number in a message are detected.
Total residual error probability for undetected corrupted messages: less than
message error rate * 4.7 * 10
-11
.
Error Signalling and Recovery Time
Corrupted messages are flagged by any node detecting an error. Such messages are
aborted and will be retransmitted automatically. The recovery time from detecting an
error until the start of the next message is at most 29 bit times, if there is no further
error.
Fault Confinement
CAN nodes are able to distinguish short disturbances from permanent failures.
Defective nodes are switched off.
Connections
The CAN serial communication link is a bus to which a number of units may be
connected. This number has no theoretical limit. Practically the total number of units
will be limited by delay times and/or electrical loads on the bus line.
Single Channel
The bus consists of a single channel that carries bits. From this data resynchronization
information can be derived. The way in which this channel is implemented is not fixed
in this specification. E.g. single wire (plus ground), two differential wires, optical fibres,
etc.
Bus values
The bus can have one of two complementary logical values: ’dominant’ or ’recessive’.
During simultaneous transmission of ’dominant’ and ’recessive’ bits, the resulting bus
value will be ’dominant’. For example, in case of a wired-AND implementation of the
bus, the ’dominant’ level would be represented by a logical ’0’ and the ’recessive’ level
by a logical ’1’. Physical states (e.g. electrical voltage, light) that represent the logical
levels are not given in this specification.
Basic Concepts