how to work with MMC 4bit mode in wince6.0

Jethin Sekhar

Hi All,

I'm facing a problem in using MMC for booting for 4/8 bit mode. I can use sd card in 4bit mode and 24Mhz but in the mmc it working only in 1 bit.

Can any one suggest an idea how boot from mmc card using 4/8bit?

The messages which i got from debug port is mentioned below.

Init HW: controller RST
SDHC: 1 bit mode
SDCARD: reqested speed 1000000, actual speed 1000000
SDHC: command response timeout CTO!
MMC::MMCCommandResponse: MMCSendCommand error, command = 8
MMC::MMCCommandResponse: Command Response Error
SDHC: command response timeout CTO!
MMC::MMCCommandResponse: MMCSendCommand error, command = 55
MMC::MMCCommandResponse: Command Response Error
SDCARD: reqested speed 25000000, actual speed 24000000

Thanks in Advance

Jethin

over 14 years ago

0 DavidVescovi over 14 years ago

Genius 5470 points

I do know MMC 8bit mode is not supported natively in Windows CE6. They did add support for MMC 8bit in WEC7.

Not sure about 4 bit.

0 DavidVescovi over 14 years ago in reply to DavidVescovi

Genius 5470 points

Also don't expect it to boot any faster if using 4bit or 8bit, it does not.

The bottleneck in the boot loader is not the data path width. I know having implemented 1, 4 and 8 bit data widths. boot time is virtually the same.

0 Jethin Sekhar over 14 years ago in reply to DavidVescovi

Expert 1130 points

Thanks David,

Do you have any idea how to implement and test the 4 bit MMC in the eboot of Win CE 6.0 with Omap 6.14 BSP?

And how your are saying there is a bottleneck in the bootloader because this is a major issue in our development.

It would be great if you share your code.

Thanks in advance.

Jethin

0 DavidVescovi over 14 years ago in reply to Jethin Sekhar

Genius 5470 points

I can't share the code but I can say its rather easy to implement. I did it for an 8bit eMMC implementation.

The bootloader polls the MMC status register for data ready. The actual data ready rate is pretty much exactlly the same wether 1bit, 4bit or 8bit.

0 Jethin Sekhar over 14 years ago in reply to DavidVescovi

Expert 1130 points

Thanks.

Is it possible to say me some steps or can i get some starting point to start the 4 or 8 bit implementation as i could not find any loop to start the implementation.

Jethin

0 Jatin Jain over 14 years ago in reply to Jethin Sekhar

TI__Genius 9185 points

Try enabling the environment variable BSP_EMMCFEATURE. At this time I don't think this flag was tested in the BSP 6.14.01 release. But atleast if you search for this you will get the places in code where this is used and give you a way forward.

As David mentioned 8 bit is not supported by WinCE6 (and the BSP code also does not have support).

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how to work with MMC 4bit mode in wince6.0