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TM4C1237D5PZ: SysCtlReset resets micro but kills USB

Manoj Kumar91
Prodigy 220 points
Part Number: TM4C1237D5PZ

Hi TI Team, 

I am trying to reset micro on hardware fault. It does reset micro but USB device disappears from Device Manager in Windows. If i do power on reset. USB device shows up. I was wondering what is the difference between SysCtlReset and POR? How can i simulate POR in the software. 

Thank you,

  • 0
    Prodigy 220 points
    Actually device appears as Unknown Device
  • 0 in reply to Manoj Kumar91
    TI__Guru**** 158815 points
    Hi,
    You can't really simulate a POR using SysCtlReset which is a software system reset. It is different from a button pressed reset or Power Up, which are treated as POR reset. A system reset does not go through the device initialization like a real POR or a simulated POR does. I think you want to investigate what caused the hard fault and how to fix it first.
  • 0 in reply to Charles Tsai
    Guru 117850 points

    Agree w/the advice of vendor's Charles - yet you may simulate "POR" by employing a GPIO to drive a FET - which pulls MCU Reset to ground.

    Note that It is often necessary to "insure" that the external FET performs as a "one-shot" - with adequate "on time" - so that the Reset pulse meets spec...    (i.e. when the MCU "feels" the Reset - the GPIO output - which initiated that reset - will end.    The external FET's gate circuit must serve as, "Fast Attack - yet Slow Decay."    (to insure adequate pulse width @ MCU's Reset.))