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Linux/AM3359: eMMC boot

Vamsi Siddhani
Expert 1420 points
Part Number: AM3359

Tool/software: Linux

We are working on a custom board based on AM3359. SDK we are using is ti-processor-sdk-linux-am335x-evm-05.00.00.15

 

1. In our schematic eMMC is connected to processor's MMC1 interface for booting the processor. For reference, the connections are mentioned here:

Sl.No.
EMMC Pins
Processor Pins
Mode
1
D0-D7
GPMC_AD8-GPMC_AD15
2
2
CMD
GPMC_CSn2
2
3
CLK
GPMC_CSn1
2
4
RSTN
GPMC_CSn0
7
5
DS
GPMC_CSn3
7

2. In TRM the below connections are specified.

Our eMMC devices has 8 data lines. but this TRM shows only 4 data lines connected to processor.

Can anyone verify that whether our connections are proper are not.

Regards

Vamsi

  • 0
    TI__Guru**** 393215 points
    Hi,

    No, eMMC boot from MMC1 will not work with these connections. Please use the Beaglebone Black schematic as a reference for the correct connections: elinux.org/Beagleboard:BeagleBoneBlack

    Additionally I strongly suggest you move the eMMC RSTn signal from GPMC_CSn0 to some other I/O. GPMC_CSn0 is used in a lot of boot sequences and may have unwanted effect on MMC1 boot.

    The eMMC DS pin can be left unconnected, as it cannot be used on AM335x devices. This signal is needed only in eMMC HS400 mode, which AM335x does not support.

    Lastly, the TRM shows only 4 data bits, because initially the processor boots from the eMMC in 4-bit mode. This is switched to 8-bit mode later in the boot sequence.