What happens if the TJA1028 receives a wake-up frame when TJA1028 is transiting to the Sleep mode.

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What happens if the TJA1028 receives a wake-up frame when TJA1028 is transiting to the Sleep mode.

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Contributor I

The TJA1028 data sheet has the following description.

7.2.5 Transition from Normal to Sleep or Standby mode

In order to ensure that the remote wake-up time (twake(dom)LIN) is not reset on a transition to Sleep mode, TXD should be pulled LOW at least td(EN-TXD) after EN goes LOW.

Q1. What happens if the TXD pin cannot be held LOW for td (EN-TXD) time?
Q2. Why does keeping the TXD pin LOW for td (EN-TXD) time ensure "the remote wake-up time (twake (dom) LIN) is not reset"?

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NXP TechSupport
NXP TechSupport

Hi Hozumi-san,

 

Please take a closer look at the attached AH1003, 5.3.1 Transition Normal to Sleep mode.

TXD should be set to Low after td(EN-TXD) from EN falling edge and keep on set to Low until tmsel(max) to enter Sleep mode.

 

Fig. 24.png

 

A1. TXD should be kept high for td(EN-TXD), then, switch to Low until tmsel(max) finishes to enter Sleep mode as shown in Figure above.

 

A2. Even in transition from Normal to Sleep, the remote wake up request from another node to be detected, but, twake(dom)LIN measurement can be reset if TXD goes low at the same time as EN.

 

Best regards,

Tomas

 

 

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Contributor I

Hi Tomas,

 

Thank you for sharing the useful document.

Does the twake(dom)LIN measurement be triggered by the falling edge of the LIN bus to the dominant?

Does this mean that if the measurement is reset, the wakeup request will be missed because the measurement will not start until the next falling edge of the LIN bus?

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NXP TechSupport
NXP TechSupport

Hi Hozumi-san,

 

1. Twake(dome)LIN is made by filter. The receiver checks if dominant longer than twake(dom)LIN was received.

2. I could not understand the actual intention of this question. How is the measurement reset? If you thought edge trigger might be reset by multi-edge, it is not the case, I think.

 

Best regards,

Tomas

 

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Contributor I

Hi Tomas,

My intention for the question "How are measurements reset?" is "What are the cases where the wakeup signal is lost when the measurements are reset?".

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Contributor I

Is there any update on this?

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