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6747 SPI SCS[0] pin doesn't work

dake zhan
Prodigy 90 points
Other Parts Discussed in Thread: TMS320C6747, TMDSOSKL137

When I was using 6747 SPI1 as master in 4-pin mode with SCS[0] pin, I found this pin doesn't work. It held high all the time.

Then I try to test this pin, using it as an GPIO output, still it can't output low level. However, it worked well as a GPIO input.

I also tested SPI0, it's pins worked well.

I carefully checked the circuit and found no connecting error. I had 3 circuits of 2 different layout versions, they all exhibit such problem.

Could anyone help on this? Is it possible to be an bug of the chip?

  • 0
    Expert 1950 points

    Hello,

    Such a bug in a mature chip (and even in a first batch one) is very unlikely; from information given, here are 2 more possibilities that generate similar symptoms:

    - misconfiguration of the pin (check value of PINMUX9 register); access to the pin state through GPIO (input) is possible in all cases

    - conflict on board with another output (voltage while outputting 0 or 1 are different)

    Jakez

  • 0
    TI__Guru 64500 points

    Do you have an EVM for the TMS320C6747 to compare to?

    Also, which pin specifically are you referencing?  Is it Pin N4, SPI0_SCSn?

    The Starter Kit (http://www.ti.com/tool/tmdsoskl137) uses the above pin for supporting connection to an on board SPI Flash device.

  • 0 in reply to Jakez
    Prodigy 90 points

    Hello,

    You are right. I was misled by the SPI datasheet, it says to use the pins as GPIO just by configuring SPIPCn registers, so I didn't consider the PINMUX. 

    I should have known it's configured as 3-stated since it can input but not output.

    Btw, the dozen of  datasheet are really a mess and lack a systematic point of view.

    Thanks a lot~

  • 0 in reply to BrandonAzbell
    Prodigy 90 points

    Hello,

    I don't have a 6747EVM，but I do have a 6713 one.

    It seems the problem is caused by my silly mistake.

    Thank you all the same.