Chapter 8 - Section 5: Controller Area Network (CAN) Bus Flashcards
1
Q
What are the data rates for a CAN bus?
A
- 1 Mbps for cable lengths <40m
- As cable length increases, the data rate falls, 125 kbps for 500 metres in length
2
Q
How are data collisions avoided on the bus?
A
Carrier Sense Multiple Access (CSMA)/Arbitration based on Message Priority (AMP) technique
3
Q
What does CSMA ensure?
A
A terminal will transmit only when the bus is quiet (no carrier)
4
Q
What happens if two or more terminals try to transmit at the same time?
A
The AMP bus arbitration logic will connect the terminal with the higher-priority message
5
Q
What is the normal limit to the number of terminals connected to the bus?
A
32 to avoid data delay
6
Q
What is the data encoding of the CAN bus?
A
Non-return to zero
7
Q
What are the advantages of the CAN bus?
A
- No separate master bus controller
- No need to retransmit a message due to non-destructive bitwise arbitration
- Only one message on the bus at any one time
- CAN bus will not collapse or lock up
8
Q
Why is there no SDI on a CAN bus?
A
Each LRU has a filter to accept only those messages relevant to it
