SLLA521B January   2022  – June 2022 TCAN1145-Q1 , TCAN1146-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction – Partial Networking
  4. 2Partial Networking Application
    1. 2.1 Modes of Operation and Partial Networking
    2. 2.2 Sleep Mode and Partial Networking
    3. 2.3 Wake-Up Frame
    4. 2.4 Classical High-speed CAN, CAN FD, and PN
    5. 2.5 Mixed Network Information
  5. 3CAN Frames and Wake-up Frames
    1. 3.1 CAN Frame Structure
    2. 3.2 Wake-up Frames
      1. 3.2.1 ID Field Match
      2. 3.2.2 Data Length Code (DLC) Match
      3. 3.2.3 Data Match
      4. 3.2.4 CRC Match
      5. 3.2.5 Acknowledge Match
    3. 3.3 Error Counter
    4. 3.4 Selective Wake FD Passive
  6. 4Selective Wake Registers
  7. 5Configuring Partial Networking
    1. 5.1 Valid CAN Message ID Example
    2. 5.2 Valid Data Example
  8. 6Summary
  9. 7References
  10. 8Revision History

2.2 Sleep Mode and Partial Networking

CAN ECUs are generally seen in three states: sleep mode (low current consumption, ≤ 100 µA), standby mode (higher current consumption, 10s to 100s mA), and normal mode (highest current consumption, 100s mA to several amps). Since each node uses significantly less current when it is asleep, the longer ECU is in sleep mode, the more power that can be saved. PN breaks sleep mode into two different levels, see Figure 2-2, allowing overall network current consumption to be reduced. When an ECU is in sleep mode, it is waiting to wake up, which can be accomplished by a WUP signal.

Figure 2-2 Partial Network in Sleep Mode

When an ECU receives a WUP, non-PN capable ECUs will wake up and transition to standby mode, whereas PN enabled ECUs will transitions to a higher sleep state, but not into standby mode. In this higher sleep state, the CAN bus bias changes from ground to 2.5 V while listening for a valid wake-up frame (WUF). This bias change is necessary for the WUF receiver to decode the CAN frames and no bus traffic is passed through to the CAN transceiver RXD pin. While the ECU is in this higher sleep state waiting for a valid WUF, only a subset of the node is awake and is consuming ~ 500 µA and not the 10s to 100s of mA that a non-PN node would be consuming.