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Original question:

AM6442: eMMC pull-ups necessary or not?

[FAQ] AM62A7: MMC0 Pull Resistor Requirements

ROBERT BONINI
Intellectual 390 points
Part Number: AM62A7
Other Parts Discussed in Thread: AM6442

This e2e exchange: AM6442: eMMC pull-ups necessary or not?, results in a statement that the AM6442 requires no external pull resistors on the MMC0 interface, and that the processor will provide all required pull levels.  Is this also the case for the AM62A processors?

  • +1
    TI__Guru 60265 points

    No. You must connect an external pull-down on CLK, and external pull-ups on CMD and DAT0 to prevent these eMMC device inputs from floating until software initializes the host controller and AM62Ax IOs associated with MMC0. The eMMC standard requires an eMMC device to have internal pulls turned on by default on DAT[7:1], so these signals do not require an external pull-up resistor. Software should turn on the respective internal AM62Ax DAT pull-ups when the bus width is increased from 1-bit mode to 4-bit or 8-bit mode.

    This is required on AM62A because the IOs associated with MMC0 are implemented with standard dual-voltage LVCMOS IO cells with the capability of multiplexing additional signal functions to the respective device pins. Therefore, these MMC0 IOs are turned off by default since it is unknow what may be connected to these pins. That is not the case for AM64x since it's the MMC0 port is dedicated to eMMC.

    Regards,
    Paul