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

2.1 Modes of Operation and Partial Networking

CAN has three main modes of operation that have a direct impact on the system power: normal mode, standby mode, and sleep mode. Normal mode is the highest power mode where CAN or CAN FD communication takes place. Standby mode is the transitional mode from sleep, where the ECU wakes up from sleep and the transceiver waits for the ECU system processor to place the CAN transceiver into normal mode. It’s important to note that standby and sleep modes do not allow data from the CAN network to be passed through to the CAN transceiver RXD pin. Lastly, sleep mode is the lowest power mode where only the CAN transceiver’s low-power receiver is active in the ECU.

When the ECUs are placed into sleep mode (low-power mode), a wake-up pattern (WUP) starts the wake up process for every node on the network. WUP is a filtered dominant pulse, followed by a filtered recessive pulse, and then by another filtered dominant pulse. WUP acts as a basic noise filtering mechanism that differentiates CAN noise from actual CAN traffic. When a CAN frame is sent over CAN, every node recognizes a WUP and transitions out of sleep mode to a higher power mode such as standby or normal modes and all CAN nodes consume current at higher levels.

When an ECU supports PN, an additional step in the wake process is required to leave sleep mode. A CAN node that supports partial networking breaks sleep mode into two states, deep sleep (CAN bus GND bias) and sleep (CAN bus 2.5 V bias). While the PN-enabled CAN transceiver is in either of these sleep states, no CAN frames are passed through to the RXD pin.