eMMC 8-bit support

Michal Solecki

Hi,

I am using a beaglebone black (AM335x) and I have been trying to enable 8-bit mode on the MMC controller to use the eMMC in 8-bit mode. The eMMC is on MMC1.
According to the TRM, I can change the mode by sending a switch command to the eMMC and setting the DW8 bit in SD_CON register to 1.

But what about the DTW bit in the SD_HCTL regsiter?
Data transfer width:
0h for 1-bit;
1h for 4-bit
but no setting for 8-bit

How does that work if my eMMC is set in 8-bit mode and the data transfer width is 4bits?

Thank you in advance

Michal

over 11 years ago

0 Miroslav Kiradzhiyski XID over 11 years ago

TI__Mastermind 25235 points

Hi Michal,

Our hardware engineer is currently on vacation, so I'll forward this to the factory team.

Best regards,
Miroslav

0 Michal Solecki over 11 years ago in reply to Miroslav Kiradzhiyski XID

Intellectual 295 points

I finally got it working.

By setting SD_CON register to 1, we automatically set the transfer mode to 8-bit. The DTW bit in the SD_HCTL register is set to 0.

After setting the transfer to 8-bit mode, the pin mux and the DMA, I am now getting 26.7MB/s transfer from the eMMC during boot-up.

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eMMC 8-bit support