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OMAP-L138 EMIF address pull-up/down

Kenji Tanaka
Prodigy 60 points
Other Parts Discussed in Thread: OMAP-L138, OMAP-L137
For customer's board design, is it mandatory to pull-down the EMIFA upper address A[18:13] as below description in the EMIFA User's Guide P74? If yes, why is it unneccesary to pull-down the other address A[12:0] and A[23:19] as well? Or is it acceptable to pull-up the A[18:13]?
> 　The upper address inputs A[18:13] are provided by GPIO pins. The
>   six GPIO pins are connected to the upper address bits of the flash
>   memory and attached to pulldown resistors so that their value is 0
>   after reset and before configuring the pins as GPIO. This is necessary
>   if the ROM bootloader is copying the secondary bootloader from theflash.
Best Regards,
Tanaka
  • 0
    TI__Mastermind 27585 points

    For OMAP-L138, GPIOs are unnecessary since there are 24 address pins. The ROM bootloader drives all 24 address pins, so there is no need to use pull-down resistors.

    For OMAP-L137, there are not enough address pins, and the ROM bootloader does not configure or drive the GPIOs. This is why you need pulldowns during boot for this device.

    Jeff