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

2.2 Restart Mode

The second mode is also transitory and is referred to as restart mode. This mode is used to finish initialization of SBC as well as acts as a landing state for selected faults. Most of the device is still in an off state during restart mode. All the voltage regulators are either on or ramping (depending on previous device state); LRXD and CRXD are held high, LIMP retains previous mode state, and the nRST pin is pulled low and depending on entry can either latch until mode change (during power up, wake, and undervoltage events) or pull low for a predefined time period then force a mode change to standby.

There are five different ways to enter into restart mode. The first is from Init mode – when VSUP has crossed the UVSUP_R threshold the device can transition to restart mode – for hard resets, POR, or power cycling this is the entry pathway. The next entrance is due to wake events while in either sleep or fail-safe mode, a wake event can transition the SBC into restart mode. The other three entryways into restart mode are from fault conditions. A UVCC1 event, which is an undervoltage event on VCC1, can cause the device to enter restart mode. If the watchdog timer failure counter exceeds the programmed threshold level, default is one failure, can cause the device to transition to restart mode. If VCC1 is enabled to be active in sleep mode a SWE timer expiration can cause the device to transition to restart mode.

There are three different ways to exit restart mode. If device is operating as expected without fault the device can transition to standby mode when VCC1 has crossed the UVCC1R threshold and sustains the voltage for t_RSTN_act signals to the SBC that VCC1 is at a ready an active state. The other two exit paths are due to fault conditions. Every time the device enters restart mode a restart counter is incremented and there is a programmable threshold for how many times device can restart before an error is flagged and the device can transition to fail-safe mode if enabled and sleep mode otherwise. By default, the reset counter can experience an overflow on the 5th device reset but this value can be changed to be larger or smaller. The other exit path is if the restart timer has elapsed and VCC1 never met the transition condition – in this case the device can transition to fail-safe mode if enabled and sleep mode otherwise.

Restart Mode Figure 2-3 Restart Mode