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

5.8 LIMP

The last protection feature that has been briefly mentioned previously is the LIMP pin which supports LIMP home functionality. The LIMP signal is an active low output that can signal a system that there is a major issue that is occurring on the device. By default, the LIMP pin can activate when there are missed watchdog triggers and won’t reset until the configured condition is met - which by default is three correct watchdog triggers after the missed watchdog trigger. This pin also can activate when the device enters into fail-safe mode alerting the system at large that there was a fault that caused the SBC to enter the fail-safe mode. This is possible to read the LIMP pin state, assuming VCC1 is active, by first enabling the read ability, which is done by setting 1A[6] = 1, then reading the LIMP state at address 1A[5].