• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 79 subscribers
  • Views 231 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430F6779A: Extanal R-pullup in SPI with flash memory

waragorn sornpanya
Prodigy 170 points
Part Number: MSP430F6779A


Tool/software:

From this post SPI operation no pull-ups are needed.

https://e2e.ti.com/support/microcontrollers/msp-low-power-microcontrollers-group/msp430/f/msp-low-power-microcontroller-forum/190323/pull-up-required-or-not-in-spi

My SPI usage involves an MSP430 as a master connected to a single flash memory.

Questions:

  1. Does the MSP430F6779A MCU require pull-up resistors for SPI communication?
  2. If pull-up resistors are not necessary for SPI, can data be read from the flash memory normally, or are special techniques required?"
  • 0
    TI__Mastermind 26080 points

    Hi Waragorn,

    The linked thread is good and lightly touched on some more nuance topics. SPI communication does not need external pull-up/down as the IOs are push-pull IOs (meaning the IOs can drive a signal, versus an open-drain IO which wouldn't be able to drive a signal).

    The comment of external or internal pull-up/down was to prevent a floating node in the scenario where the other attached device was not initialized, connected or powered. Floating nodes can consume extra current as you can go into a state where the transistor is in-between states due to system noise and the floating node can cause leakage. Putting a pull-up/down on the MISO (SOMI) will prevent the node from floating and will give the pin a defined state.

    Data will be able to be read from the external flash through normal operation, I would double check your external flash memory to check for any specifics on their end but the MCU side won't care about pull-up/down.

  • 0 in reply to Luke Ledbetter
    Prodigy 170 points

    Can SPI signals still be used if they're combined with port mapping and no pull-up resistors are included?

  • 0 in reply to waragorn sornpanya
    TI__Mastermind 26080 points

    Hi Waragorn,

    What do you mean with the combined with port mapping comment? Are you intending to change the function of the pins in real time?

  • 0 in reply to Luke Ledbetter
    Prodigy 170 points

    I need to configure port mapping during initialization because my SPI pins are not assigned to the default peripheral function.

    Example pin connection.

    Do we need pull-ups on SCK, SDI,SDO on the lines.

  • 0 in reply to waragorn sornpanya
    TI__Mastermind 26080 points

    Hi Waragorn,

    You won't see a large benefit by adding the external resistors for the small time the device is initializing the pins. Once the SPI and pins are setup to use SPI then spi will be functional.

**Attention** This is a public forum