SLLA651 April   2025 TCAN2845-Q1 , TCAN2847-Q1 , TCAN2855-Q1 , TCAN2857-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Device States
    1. 2.1 Init Mode
    2. 2.2 Restart Mode
    3. 2.3 Standby Mode
    4. 2.4 Normal Mode
    5. 2.5 Sleep Mode
    6. 2.6 Fail-Safe Mode
  6. 3Power Electronics
    1. 3.1 VSUP
    2. 3.2 VHSS
    3. 3.3 VCAN
    4. 3.4 VCC1
    5. 3.5 VCC2
    6. 3.6 VEXMON, VEXCTRL, and VEXCC
    7. 3.7 HSSx
  7. 4Communication Capabilities
    1. 4.1 CAN-FD and Classical CAN
    2. 4.2 CAN-SIC
    3. 4.3 LIN
  8. 5Protection Features
    1. 5.1 Undervoltage (UV) Monitors
      1. 5.1.1 VSUP
      2. 5.1.2 VHSS
      3. 5.1.3 VCAN
      4. 5.1.4 VEXCC
      5. 5.1.5 VCC1
      6. 5.1.6 VCC2
    2. 5.2 Overvoltage (OV) Monitors
      1. 5.2.1 HSSx
      2. 5.2.2 VCC1
      3. 5.2.3 VCC2
      4. 5.2.4 VEXCC
    3. 5.3 Short Circuit (SC) Monitors
      1. 5.3.1 VCC1
      2. 5.3.2 VCC2
      3. 5.3.3 VEXCC
    4. 5.4 Electrical Faults and Impact on SBC Mode
    5. 5.5 Temperature Sensors
    6. 5.6 Watchdog
      1. 5.6.1 Watchdog Error Counter
      2. 5.6.2 Timeout
      3. 5.6.3 Window
      4. 5.6.4 Initial Long Window
      5. 5.6.5 Q&A
    7. 5.7 Communication Fault Monitoring
      1. 5.7.1 CAN
      2. 5.7.2 LIN
    8. 5.8 LIMP
  9. 6Programming, Memory, and Control
    1. 6.1 SPI
    2. 6.2 EEPROM
    3. 6.3 Interrupts
    4. 6.4 Control
  10. 7Miscellaneous Features
    1. 7.1 Local Wake Ups
    2. 7.2 CAN Bus Wake Up (BWRR)
    3. 7.3 Partial Networking
    4. 7.4 GFO, nRST, and SW
  11. 8Summary
  12. 9References

5.7.1 CAN

The CAN bus is monitored for 7 different fault conditions on the TCAN28XX line of devices; these are all captured in the CANBUS interrupt register (54h).

Table 5-4 CAN Bus Interrupts on TCAN28xx Devices
Bit Field Flag Description
7 UVCAN UV Event on VCAN
6 RESERVED N/A
5 CANHCANL CANH and CANL shorted
4 CANHBAT CANH shorted to battery
3 CANLGND CANL shorted to GND
2 CANBUSOPEN CAN Bus Opened
1 CANBUSGND CANH shorted to GND or both CANH and CANL shorted to GND
0 CANBUSBAT CANL shorted to VBAT or both CANH and CANL shorted to VBAT

From the interrupts that are monitored this needs to be clear that the fault types are not exhaustive and an interrupt alone generally does not give all the information an end designer wants or needs to know. To highlight this concept, ten different fault cases can be used to show what interrupts are registered and what information can be gathered from each fault at the SBC.

Table 5-5 CAN Bus Fault Scenarios
Fault # CANH CANL Fault Detected Comment
1 Open Open CANBUSOPEN N/A
2 Open Normal CANBUSOPEN SBC cannot tell difference between fault 1 and 2
3 Normal Open CANBUSOPEN SBC cannot tell difference between faults 1,2, and 3
4 Shorted to CANL Shorted to CANH CANHCANL N/A
5 Shorted to VBAT Normal CANHBAT N/A
6 Shorted to GND Normal CANBUSGND N/A
7 Normal Shorted to VBAT CANBUSBAT N/A
8 Normal Shorted to GND CANLGND N/A
9 Shorted to GND Shorted to GND CANBUSGND SBC cannot tell difference between faults 6 and 9
10 Shorted to VBAT Shorted to VBAT CANBUSBAT SBC can’t tell difference between faults 7 and 10

With interrupt map explored for CAN faults this needs to be clear that the SBC can tell the controller through an interrupt that there is an issue – and give some information on the fault – but this does not necessarily give all pertinent information about location and does not even give enough information to determine the pin that is at fault depending on exact fault scenario.

One fault that hasn’t been talked about is the dominant timeout fault. At the logic input pin, CTXD, if the level is set near GND and the device doesn’t detect a rising edge on this pin for 1ms (min) to 5ms(max) the CAN driver is disabled to prevent stuck bus conditions.