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Internal pull-up/down resistors in power off state

Brandon Gardner
Prodigy 220 points


Do the MSP430 internal pull-up/down resistors function when the device is in a power off state? I have found that the internal resistors on my F5659 are disabled upon power up.

Thanks,

Blaine

  • 0
    Guru 46710 points

    Brandon Gardner said:
    Do the MSP430 internal pull-up/down resistors function when the device is in a power off state?

    As pull-up/down resistors are software-configurable - how they know their state (configuration) when device have no power? Do software work while CPU powered off?

  • 0 in reply to Ilmars
    Guru 58965 points

    In LPM6 (or LPMn with n>6), all pins act like a pull-down resistor -- some weak, some strong.

  • 0
    Guru 227245 points

    If a device intentionally enters LPM3.5 or 4.5, the I/O pin configurations, including resistor settings, are preserved and the pins remain in their current state.

    Upon wake-up, the registers are locked and the previous state is held until the firmware explicitly unlocks the registers. The power-on configuration by the core boot code has no effect until the registers are unlocked by the application code.
    If the MSP shuts down due to power-loss, the port logic is unpowered, and all circuitry more or less acts as pull-up or pull-down to GND or VCC (which is 0V then too). Including the protection (clamp) diodes, which short any input voltage >VCC+0.3V to VCC (and since VCC is 0V then...)

    On power-up, the port logic will initialize with resistors disabled and port in input direction (high-Z)

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