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Original question:

TCAN2451-Q1: JLINK tool can't be connected to MCU when using tcan2451 nRST(mornitor pwr-down voltage) function.

TCAN2451-Q1: JLINK tool can't be connected to MCU when using tcan2451 nRST

Josh Guo
Prodigy 10 points
Part Number: TCAN2451-Q1

Tool/software:

i met the same issue. it seems like when the sbc in standby mode, if the JLINK try to connect mcu via pull down rst pin, the sbc will transfer to Init mode,  then hold nRST about 60ms.

the yellow line is SWD connector RST signal, the green line is  SWD connector SWDIO signal.

JLINK try to connect MCU, but not match SBC TCAN2451 nRST output.

  • 0
    TI__Guru 52262 points

    Hi Josh,

    From what I remember on the last similar issue is that you have to disconnect the nRST pin from the SBC for the tool to work properly - we don't design these devices to necessarily work with J-LINK - so we don't guarantee compatibility - but the nRST pin on the SBC is bi-directional so it could be sending a signal that causes issues - please if you could remove R1 and retry I think you will see better results because I do think there is a compatibility issue when you connect nRST to the RST pin of the J-LINK tool. 

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Prodigy 10 points

    If I remove R1，the JLink tools work well. I do not think it was compatibility issue.when the TCAN2451 is in standby mode ,it should ignore nRST input signal.

    if TCAN2451 not output nRST signal when JLINK connect mcu, it will be ok.

  • 0 in reply to Josh Guo
    TI__Guru 52262 points

    Josh,

    It is a compatibility issue - the nRST pin acts as an output when the SBC goes into restart mode - that is why the tool has trouble reading it. 

    In every other mode when VCC1 is active the nRST pin acts as an input - in those modes the J-LINK tool has been found to work from past issues reported to us. 

    the Soft reset isn't the nRST reset - soft reset is done purely in software. 

    Best,

    Parker Dodson