Interview questions on CAN protocol

1.   What is CAN?
2.   What is Asynchronous Serial Communication?
3.   Why CAN is reliable?
4.   How many layer it supports?
5.   What is the max speed of CAN?
6.   St. CAN vs Extd. CAN? Can they coexist on a network?
7.   If they can co-exist, which one will have priority; if not, what is the reason?
8.   Describe the process of bus arbitration in CAN?
9.   What's the difference between CSMA/CR and CSMA/CD?
10. How can we identify a specific sensor in a CAN network?
11. Data Frame vs Remote Frame; Who wins arbitration? Explain why?
12.  What is bus termination resistor value for CAN? Do they vary if we put them in each node instead of bus ends?
13. Explain Error Frame? Explain the error states (Like Passive Active and Bus-off)?
14.  What is BUS-Off? What happens when bus-off occurs?
15. What is TEC and REC?
16. How they increment and decrement?
17. What is difference between Inter frame space and overload frame?
18. What is time quanta?
19. Explain
20. How does CAN work? What are the features of CAN?
21. Why SOF is always a dominant bit?
22. Explain error detection mechanism?
23. CANALyzer vs CANoe
24. CAPL vs IG
25. IG block vs G block
26. How many nodes can be simulated in Canalyzer and Canoe?
27. Data frame vs Remote frame? Who wins when both are available in the network?
28. What is Bit-Encoding?
29. What is bit-stuffing?
30. Why bit stuff happens after 5th bit; why not after or before 4th or 6th bit?
31. What is DLC? Why is it needed?
32. CAN vs LIN?
33. CAN vs KWP vs UDS?
34. Why 7F has considered for €“ve response why not other than 7F?
35. What is tester present? Why do we need it?
36. What is security Access? Why do we need it?
37. What is CANCaseXL (if you have used it)? Explain with types?
38. If there are only two nodes on the bus, and both are transmitting same    identifier(exactly the same identifier),who will win the arbitration or what happens?
39. If there is only one node on the bus and it is transmitting messages on the bus continuously, what will happen? Is node will go into the bus-off state or what happens?
41. Is CAN full duplex? what is the significance of Extended frames other than that it can be used for generating more identifiers?
42. What is the major difference between CAN 2.0B and previous version?
43. Without CAPL,can we simulate the other ECU's CAN Messages except Test ECU in the CAN Simulation Network in CANoe tool without using IG or G blocks.
44. How many can database files are required for CAN Network simulation in CANoe tool.
45. what is the difference between CANalyzer,CANoe and CANape tools?
46. Mention the few uses of the CANoe tool?
47. what is a panel is CANoe Tool and its Use?
48. Why CAPL scripting is used in CANoe tool?
49.   Is it possible to simulate other ECU's Except Test ECU without CAPL Scripting in CANoe tool?
50. What is flow control frame?

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  1. Answer for q:39

    There is only one node on the bus and it transmitting messages continuously, but there is no another node on the bus to receive the can messages so the tranmitting node continuously receiving the ack error and re transmit the messages again..untill receive the correct ack and error frames are transmitted on the bus. finally that node go to bus off state.

    1. @sreekanth. in this case node does not reach bus off state. it just reaches Error passive

    2. When any one of the two Error Counters raises above 127, the node will enter a state known as Error Passive and when the Transmit Error Counter raises above 255, the node will enter the Bus Off state