Information Technology Reference
In-Depth Information
4. CAN_L shorted to ground.
5. CAN_H shorted to ground.
6. CAN_L shorted to battery voltage.
7. CAN_L shorted to CAN_H wire.
8. CAN_H and CAN_L interrupted at the same location.
9. Loss of connection to termination network.
A fault tolerant network will be able to survive these faults, and still transmit data (although
the SNR will be reduced). An 82C250-type transceiver may not be able to survive many of
the conditions. Fault-tolerant drivers, such as the TJA1053, can handle these failures (though
at a reduced maximum speed).
21.7 CAN open
The CAN Application Layer (CAL) was originally developed by CiA and involves:
•
CMS (CAN-based message specification) - defines protocols for transferring data be-
tween CAN modules.
•
NMT (network management service) - defines the protocols for system start-up and
shutdown and error logging.
•
DBT (distributor service) - defines a protocol for distributing identifiers to the different
modules in a system.
21.8 Exercises
21.8.1
In the CAN bus, what is the basic bit rate:
(a)
125 kbps
(b)
1 Mbps
(c)
10 Mbps
(d)
100 Mbps
21.8.2
Which of the following best describes a dominant bit:
(a)
A bit, that when transmitted will be overruled by a recessive bit
(b)
A bit, that when transmitted will overrule a recessive bit
(c)
A bit that is always a high level
(d)
A bit that is always a low level
21.8.3
Which of the following best describes a recessive bit:
(a)
A bit, that when transmitted will be overruled by a dominant bit
(b)
A bit, that when transmitted will overrule a dominant bit
(c)
A bit that is always a high level
(d)
A bit that is always a low level
