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How to detect the basic wake-up signal w/ TLE9351 CAN-FD transceiver

How to detect the basic wake-up signal w/ TLE9351 CAN-FD transceiver

YasA
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CAN-FD transceiver can only detect Wake-Up Pattern (WUP). However, ‘short’ CAN activity filter time can be used to also detect basic wake-up signal in HS-CAN network


Specification and detection mechanism for basic wake-up signal

CAN transceiver is compliant to ISO 11898-5 and supporting the basic wake-up signal.
The below is a specification of basic wake-up signal in ISO 11898-5.

YasA_0-1680672470982.png

To detect the basic wake-up signal, one dominant signal is needed.

And, the filter time is also defined as below

YasA_1-1680672526996.png

 

TLE7251 CAN transceiver is supporting above basic wake-up signal and the wake-up filter time. So, if dominant signal >5us is received in low power mode, it is detected as a wake-up signal.

Specification and detection mechanism for WUP

TLE9351 CAN-FD transceiver is fully compliant to ISO 11898-2;2016 and supporting the WUP.

The below is a specification of WUP in ISO 11898-2;2016,

YasA_2-1680672561677.png

To detect the WUP, the signals of dominant -> recessive -> dominant is needed.

And, the filter time is also defined as below

YasA_3-1680672589247.png

 

TLE9351 CAN-FD transceiver is supporting above WUP mechanism and both filter times. This means, the signal of dominant and recessive can be detected with only 1 bit(500kbps = 2us = 1bit > 1.8us).

In case of HS-CAN frame format of CBFF(Classical Base Frame Format), in order to detect a WUP, 2 frames are needed in theoretical worst case scenario as below

YasA_4-1680672673904.png

However, CAN-FD transceiver can be detected WUP within the 1 frame in real HS-CAN frame format.

Because absolutely there is dominant state of >1bit and recessive state of >1bit in the identifier field.

This means, in the real communication, stuff bit will be added when same bit state is sent consecutively 5bit as below,

YasA_5-1680672701609.png


Note : Even if communication bit rate is used w/ 2Mbps or 5Mbps, 500kbps is used in arbitration phase.

More information

  • ISO 11898-2;2016   (Link)
  • TLE9251xx   (Link)
  • TLE9252Vxx   (Link)
  • TLE9255Wxx   (Link)
  • TLE9351 series   (Link)
  • Lite SBC series   (Link)
  • Mid Range+ SBC series   (Link)
  • MCP SBC series   (Link)
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