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SK-AM64B: TCA6424ARGJR for BOOTMODE

Huynh Nguyen
Prodigy 240 points
Part Number: SK-AM64B

Hello,

Question of how to configure TCA6424ARGJR for POWER ON (POR) BOOTMODE without using external TEST AUTOMATION connector in the real design ?

Requirement of changing BOOTMODE from UART to OSPI and vice versa etc. by configuring the I2C IO Expander device above. The programming of the device for the proper IO level

is done before the POR cycle is initiated (under SoC/MCU I2C control). But if the power is recycled then the IO of the device is Hi-Z and Input direction as per spec and the previously programmed

information is lost. 

So how the proper IO signal levels are retained in the POR ? Or will it work only in WARM Reset mode only and P/S has to be maintained ?

Will Warm Reset work in BOOTMODE as well as in Hard Reset ?

Thanks

  • 0
    TI__Guru*** 147821 points

    Hi Huynh,

    I am routing your query to our hardware expert to comment.

  • 0 in reply to Bin Liu
    TI__Guru**** 158889 points

    Hi Huynh,

    The Bootmode configurations are latched when the PORZ_Out goes high, This is the cold reset status output.

    TCA6424ARG output should be available before latching and may needs alternative interface.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Prodigy 240 points

    Thanks for quick response. However; I would like to make sure to understand 2 scenarios :

    1. Power is recycled (power loss) : meaning TCA6424ARG preprogrammed values were not available due to cold power applied. In this case; it is required alternative interface for BOOTMODE (beside the default strapping) as your statement. Is it correct ?

    In this scenario the system will boot with the default strappings when the P/S is recycled. The SoC will then program the desire values to TCA6424ARG and issue the PORZ_OUT the second time to let it boot to the new setting. Is it workable ?

    2. TCA6424ARG needs to maintain a separate P/S other than the system power to guarantee it retains the programmed values when system power is recycled.

    Your thoughts ?

    Regards;

    Huynh

  • 0 in reply to Huynh Nguyen
    TI__Guru**** 158889 points

    Hello  Huynh,

    Thank you.

    I marked the boot mode implementation on the EVM below.

    Resistors provide the boot configuration when I2C expander is not programmed/

    Huynh Nguyen said:

    1. Power is recycled (power loss) : meaning TCA6424ARG preprogrammed values were not available due to cold power applied. In this case; it is required alternative interface for BOOTMODE (beside the default strapping) as your statement. Is it correct ?

    In this scenario the system will boot with the default strappings when the P/S is recycled. The SoC will then program the desire values to TCA6424ARG and issue the PORZ_OUT the second time to let it boot to the new setting. Is it workable ?

    The Boormode pins are inputs during power-up without internal pullup or pulldown.

    The default configuration definition is the configuration that is required for the board to start-up and function.

    The required boot configuration is expected to be stable before the cold reset MCU_PORz is released.

    The SoC programming the I2C expander is customer implementation and should be possible. 

    Huynh Nguyen said:
    2. TCA6424ARG needs to maintain a separate P/S other than the system power to guarantee it retains the programmed values when system power is recycled.

    The SoC should be cold reset to latch new boot configuration.

    Implementation is customer dependent and if the I2C expander can retain the programmed state and the SoC can be cold reset, done see any issue.

    Regards,

    Sreenivasa