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TCAN1043A-Q1: state recognition

Part Number: TCAN1043A-Q1

Hello team,

1. What is the method for the microcontroller to recognize that it has transitioned from Sleep state to Standby state through a wakeup event?

2. What is the method for the microcontroller to recognize that it is in Standby state?

3. Please fill in the table below. What I want to know is how to estimate each state transition with an external microcontroller. I have listed INH, nFault, RXD as examples, but please add columns/rows if necessary.

State INH nFault RXD
Standby H      
Normal H      
go-to-sleep H      
Sleep L      

Regards,

Hirata

  • Hi Hirata-san,

    In a typical system the MCU will be off when the transceiver is in sleep mode. At the same time, the Vio and Vcc supplies will be disabled so only the INH signal (referenced to Vsup which remains active in sleep mode) will be available. The nFAULT and RXD outputs from the transceiver will be high impedance when Vio is not supplied. 

    When the TCAN1043A wakes from sleep mode into standby and Vio becomes available the nFAULT pin will be asserted low to indicate the presence of the WAKERQ flag. During this time the MCU should be starting up as Vio just became available. The startup routine should include sampling the nFAULT state to confirm that the transceiver has woken into standby mode. Once the startup in complete, the MCU can drive EN and nSTB high to place the transceiver into normal mode and check the nFAULT status again. If nFAULT clears high when entering normal mode this indicates the wake source was a remote wake from the CAN bus. If nFAULT remains asserted low after transitioning to normal mode this indicate the wake source was a local wake on the WAKE pin or a POR condition on Vsup. nFAULT will clear once the node starts transmitting data on TXD. 

    When moving into sleep mode, the MCU should expect to lose power after some time as INH will be turned off and Vio will become unavailable. During this time after nSTB in driven low, the MCU should continue to monitor the nFAULT state. Before the transition to go-to-sleep mode, the nFAULT signal should be high. Once the transceiver begins its transition to sleep mode, any assertion on nFAULT will indicate a wake request and a transition into standard mode. If the MCU sees the nFAULT signal go low during this time, it should initiate its startup routine as it will not lose power as expected. 

    Let me know if this answers the questions you have and if there is anything else I can elaborate on.  

    Regards, 
    Eric Schott

  • Hi Eric-san,

    Thanks for your answer.

    I will communicate based on your feedback.

    I appreciate your support.

    Regards,

    Hirata