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[FAQ] AM6442: AM6442 MMC1

Jithesh Balan
Intellectual 440 points

Part Number: AM6442

Tool/software:

Hi Team,

We are using AM6442 for our new design. We are connected eMMC to MMC0 and we want to connect wifi module's SDIO signals to MMC1. Wifi module SDIO signal voltage level is 1.8v. We just want to confirm what is the voltage level in MMC1 soc side? is that 1.8V of 3.3V? if its 3.3v, how we can change to 1.8V I/O level. 

  • 0
    TI__Guru 64745 points

    The AM64x MMC1 CLK, CMD, and DAT[3:0] signal functions are implemented with SDIO buffers on pins powered from VDDSHV5, which can be operated at 1.8V or 3.3V.

    The AM64x MMC1 SDCD and SDWP signal functions are implemented with LVCMOS buffers on pins powered from VDDSHV0, which can be operated at 1.8V or 3.3V.

    The SDIO buffers were designed to support dynamic voltage change. This was necessary since UHS-I SD Cards begin operating with 3.3V signaling and changes to 1.8V signaling when the SD Card is told to transition to one of the higher speed data transfer modes. For SD Card applications the VDDSHV5 power rail is typically connected to the output pin of the internal SDIO_LDO, where this LDO defaults to 3.3V and is changed to 1.8V by the MMCSD host controller at the appropriate time.

    Note: The SDCD and SDWP signal functions were assigned to pins associated with a fixed 1.8V or 3.3V power rail (VDDSHV0). A fixed IO voltage was needed for these signal functions to maintain a stable logic state going into the MMCSD host controller when the IO voltage is changed for the other signal functions. These signal functions only connect to an external mechanical switch and pull-up, so the fixed voltage VDDSHV0 power rail was a better option for powering pins associated with these signal functions.

    In your application, you should power VDDSHV5 from the same fixed 1.8V or 3.3V power source that is being used to power the IOs of the WiFi module.

    Note: Most of the AM64x IOs are turned off by default and they will not be turned on until the system has booted and software configures them. Therefore, you may need external pulls on any signals connected to the inputs of attached devices to prevent floating inputs.

    Regards,
    Paul