Advanced CAN Bus test (Advanced)

Sample questions

5 sample questions from the Advanced CAN Bus test, with the answers. Samples are taken out of the live test, so you will not meet these when you sit it.

1. In an SAE J1939 project, which addressing mode is used for ECU identification and how does it resolve conflicts between ECUs with the same NAME?

   1. Dynamic addressing using CAN FD frame IDs for ECU identification.
   2. Static addressing with fixed PGNs assigned by the manufacturer.
   3. Address claim (PGN 60928) with a 64-bit NAME; lower NAME value wins a conflict. Address 254 = null, 255 = global.
   4. Addressing via CAN ID arbitration; lower ID values have higher priority.

   Answer: C. Address claim (PGN 60928) with a 64-bit NAME; lower NAME value wins a conflict. Address 254 = null, 255 = global.

   SAE J1939 uses address claim (PGN 60928) with a 64-bit NAME for ECU addressing. The lower NAME value wins in case of a conflict. Addresses 254 and 255 have special meanings (null and global, respectively). The other options refer to incorrect addressing modes or concepts that do not exist in SAE J1939.

2. How is a session type switch initiated in UDS over CAN?

   1. The session type switch is negotiated during the initial boot-up of the ECU.
   2. The session type switch is initiated by the tester sending a DiagnosticSessionControl (0x10) request with the desired session type.
   3. The session type switch is automatically triggered by the ECU based on predefined conditions.
   4. The session type switch is initiated by the ECU sending a DiagnosticSessionControl (0x10) request with the desired session type.

   Answer: B. The session type switch is initiated by the tester sending a DiagnosticSessionControl (0x10) request with the desired session type.

   In UDS over CAN, the session type switch is explicitly initiated by the tester sending a DiagnosticSessionControl (0x10) request with the desired session type. The ECU must then respond with a positive confirmation or a negative response. The other options are incorrect as they describe unrelated processes or misrepresent the UDS session switching mechanism.

3. Which of the following statements correctly describes how Com interacts with the CAN driver in the AUTOSAR communication stack?

   1. Com uses CanTp to communicate directly with the CAN driver.
   2. Com uses PduR and CanIf to communicate with the CAN driver, not directly.
   3. Com communicates with the CAN driver through CanSM and CanNm.
   4. Com communicates directly with the CAN driver without any intermediaries.

   Answer: B. Com uses PduR and CanIf to communicate with the CAN driver, not directly.

   In the AUTOSAR CAN communication stack, Com does not communicate directly with the CAN driver. Instead, it uses PduR (PDU Router) and CanIf (CAN Interface) as intermediaries. This layering ensures proper routing and handling of data packets within the system.

4. Which of the following best describes the appropriate use case for CAN FD and LIN in in-vehicle network communication?

   1. Both CAN FD and LIN are preferred for high-speed, large-payload data transmission in all applications.
   2. LIN is preferred for high-speed, large-payload data transmission, while CAN FD is used for low-cost, simple sensor and actuator control.
   3. CAN FD is preferred for high-speed, large-payload data transmission, while LIN is used for low-cost, simple sensor and actuator control.
   4. CAN FD is preferred for low-cost, simple sensor and actuator control, while LIN is used for high-speed, large-payload data transmission.

   Answer: C. CAN FD is preferred for high-speed, large-payload data transmission, while LIN is used for low-cost, simple sensor and actuator control.

   CAN FD supports higher data rates (up to 5 Mbit/s) and larger payloads (up to 64 bytes), making it suitable for applications that require high-speed and large data transfers. LIN, on the other hand, is a low-cost, single-master protocol ideal for simple control applications such as sensors and actuators. CAN FD is not suitable for low-cost, simple applications, and LIN does not support high-speed or large-payload data transmission.

5. Which of the following statements about the sequence number in an ISO-TP message is correct?

   1. The Flow Control (FC) frame is used to carry the sequence number in an ISO-TP message.
   2. The sequence number in an ISO-TP message is 8 bits long.
   3. The first Consecutive Frame (CF) in an ISO-TP message uses a sequence number starting at 0.
   4. The first Consecutive Frame (CF) in an ISO-TP message carries a 4-bit sequence number starting at 1.

   Answer: D. The first Consecutive Frame (CF) in an ISO-TP message carries a 4-bit sequence number starting at 1.

   In ISO-TP, the first Consecutive Frame (CF) carries a sequence number starting at 1, not 0. This is a key detail in the protocol. Other options are incorrect because: (1) the Flow Control (FC) frame is used to manage the transmission flow, not the CF; (2) the first CF uses sequence number 1; and (3) sequence numbers are 4 bits, not 8 bits.