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The definition of GPIO state on AM3352

Nomo
Guru 16800 points

Hello,

Please let me know the definition of BALL RESET STATE and BALL RESET REL. STATE described on page 17 of datasheet.
In datasheet, "H" means High-impedance with an active pull-up resistor.
Therefore, the GPIO pin which has the "H" state should be High during executing ROM code, because the ROM code doesn't change IO state.
However, some GPIO pins such as gpio1_28 (U18 on ZCZ) is 1V or 2V during executing ROM code.
GPIO connects to the FET gate pins; therefore the voltage shouldn't be dropped.

Could you tell me why the voltage drops?

Best Regards,

Nomoto

  • 0
    TI__Guru**** 161600 points

    Hi Nomoto,

    Yusuke Nomoto said:
    Therefore, the GPIO pin which has the "H" state should be High during executing ROM code, because the ROM code doesn't change IO state.

     In the example you gave, gpio1_28 is muxed with gpmc & mmc2 signals. If your device is set to boot from GPMC or MMC, ROM code can change the IO state of the pad & use ball state different than the ball reset state listed in Table 4-1. Ball Characteristics.

    Best Regards,

    Yordan

  • 0 in reply to Yordan Kovachev
    Guru 16800 points

    Hello Yordan-san,

    Thank you for your reply.

    My customer's SYSBOOT setting is 0100XXXXXX110111.
    1 means that the pin is connected 3.3V via 100k ohm resistor.
    0 means that the pin is connected 0V via 10k ohm resistor.
    X means that the pin is open (no pull-up and pull-down resistor).

    Therefore, MMC0, SPI0, UART0 and USB0 are the boot sources.
    gpio1_28 is muxed with the mmc2 signal, and it is not MMC0.
    I think that MMC2 doesn't not effect to MMC0's pin.

    Best Regards,

    Nomoto

  • 0 in reply to Nomo
    TI__Guru**** 393215 points

    Can you post the schematic with what is connected to this pin? Note that the internal pullups are relatively weak, providing approx. 100uA of current.