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Linux/AM5716: MMC3 in SDR50 mode

vamshi krishna gajjela
Expert 1695 points
Part Number: AM5716

Tool/software: Linux

Hi team,

Its clear from TRM that we can use MMC3 in SDR50 (1.8V IOs) mode, but from silicon errata i887 max clock can be 64MHz. 

Does MMC3 needs I/O cells control for choosing supply voltage from 1.8V or 3.3V ? or by writing to AC12 or HCTL it will adjust the I/O voltages. (Assuming LDO out of PMIC cable of 1.8/3/3 connected to vddshv7)

For MMC1 there is I/O control @ Table 18-1022. CTRL_CORE_CONTROL_PBIAS, how can we achieve this for MMC3 to switch to SDR-50 from HS mode.

What is the significance of MMC1 having dual-volt?

Thanks,

Vamshi G.

  • 0
    TI__Guru**** 393215 points
    The factory team have been notified. They will respond here.
  • 0 in reply to Biser Gatchev-XID
    TI__Guru 60965 points

    The I/O cells implemented for MMC1 are different than the I/O cells implemented for MMC2, MMC3, and MMC4. The PBIAS and I/O cells used on MMC1 were used successfully on previous TI devices. New I/O cells capable of supporting dynamic voltage change were developed for this device and used on MMC2, MMC3, and MMC4. The original approach was carried over to this device on MMC1 to insure dynamic voltage change worked as expected on at least one port.

     

    For details related to supply voltage switching procedure, refer to the Bus Voltage Selection section in the eMMC/SD/SDIO chapter of the TRM. The flowchart shown in Figure 25-48 describes the procedure for MMC2, MMC3, and MMC4. There is a note attached to one of the flow chart blocks that references the PBIAS registers in the Control Module. This note applies when using MMC1.

     

    To support dynamic voltage change, the I/O supply of both devices and all pull-up resistors associated with that port would be connected a power supply capable of sourcing 3.3 volts initially and able to change to 1.8 volt when appropriate.

     

    Regards,

    Paul