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TMS570LS3137: nRST driven low right after POR_RST release

Gunter Schmer
Genius 13667 points
Part Number: TMS570LS3137

Hi,

one of my customers boards is using the TMS570LS3137 and right after POR_RST is released, the nRST gets driven low. The behavior is such the nRST really never goes high, so the TMS570 must be driving the nRST low very early on. There is a table in the TRM, Table 2-8 which describes the Reset Causes upon which the TMS570 is driving nRST low.

[] Are there any other causes where the MCU is driving nRST low outside of the table 2-8?

[] Which of the table 2-8 reasons would cause nRST to stay low, even after PORRST is released from reset? I.e. which reasons would occur very early on? Oscillator failure, Voltage Monitor ...?

[] Why could the nRST not rising?

Thanks,

--Gunter

  • 0
    TI__Guru**** 186236 points
    Hi Gunter,

    The nRST is a bidirectional signal. The external circuit can assert a device reset by forcing the signal low. TI recommends that an external pullup resistor is connected to this terminal.

    The causes of warm-reset:
    1. PORRST
    2. Oscillator fail
    3. Watchdog exception
    4. Software reset
    5. External reset

    Regards,
    QJ
  • 0 in reply to QJ Wang
    TI__Genius 13667 points
    Hi QJ,

    thanks for the feedback. I think the customer has a 10k PU on nRST, but let me confirm.

    The customer has one bad board that exhibits the behavior where the nRST does not rise after the POR_RESET is released. All the other boards are ok, where the nRST goes high after POR_RESET de-assert.

    Assuming there is a PU, and the nRST does not go high, which of the warm reset causes are most likely, i.e. the nRST stays low, so something must have happened right away ...

    Thanks,
    --Gunter
  • 0 in reply to Gunter Schmer
    TI__Genius 13667 points

    Hi QJ,

    sorry, I need to check again: if the nRST does not go high, and stays low, something must have happened right away. Which of the warm reset causes are most likely?

    We are trying to figure out if this is a chip issue, since it only occurs on one board so far. All the other boards are fine and nRST rises as expected.

    Regards,

    --Gunter