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CCS/TMS320F28335: Could we not use SPISTE(SPI slave transmit-enable pin) in master mode?

user6034716
Intellectual 600 points
Part Number: TMS320F28335
Other Parts Discussed in Thread: ADS7253

Tool/software: Code Composer Studio

Hi,

According to the TRM,SPISTE is the SPI slave transmit-enable pin. Now, if it's in Master mode, could we not use SPISTE and configure the SPISTE pin  as a GPIO for other purpose?

The second question is ,  if I use SPISTE, how could I output high/low by SPISTE like a GPIO?

Thanks,

Peter

  • 0
    Expert 1940 points

    Peter,

    Yes, you are not required to use SPISTE in master mode.  I commonly omit this function and implement chip select lines in software using GPIOs so I can have multiple slaves on my SPI bus.

    A GPIO pin can either have a peripheral function like SPISTE or it can be a GPIO.  You can switch between GPIO and peripheral functions by changing the gpio mux registers and this can be run in the middle of your application execution if you so desire.

    Best,

    Trey

  • 0 in reply to Trey German8
    Intellectual 600 points

    Hi Trey,

    Thanks for your reply. I just got information from other post reply that the ADS7253 we use now needs SPISTE to generate /cs edge to define the frame(shown in following picture. Then,my question now is how to make SPISTE generate the pulse sequence ADS7253 needs. Does it generate automatically after I set up the SPI?

  • 0 in reply to user6034716
    Expert 1940 points

    Yes, the SPI peripheral will automatically generate the SPISTE signal and you can use that as your CS signal if the ADS7523 is the only other device on the SPI bus.  If you have multiple devices on the same SPI bus you will need to implement the CS signals in software using GPIOs.

    Trey

  • 0 in reply to Trey German8
    Intellectual 600 points

    Hi Trey,

    Thanks for your detail reply.

    Peter