The Micro SD card speed class on AM335x

Cosmo Yu

Hi Biser,

The TRM of AM335x show its maximum SD Speed is 24MB/S. But the Micro SD card speed class(2,4,6,10,UHS Speed Class1) only define its minimum transfer speed. I am still confused after I searched the topic about the Micro SD card.

And it seems there are four types of Micro SD card: microSD, microSDHC, microSDXC, UHS-I Cards.

Pls help confirm which type and which class Micro SD card can be used on AM335x for booting ROM.

I found one TI employee mentioned one SanDisk extreme high speed card as below picture. Which kind of Micro SD card is it?

http://e2e.ti.com/support/dsp/sitara_arm174_microprocessors/f/791/t/195143.aspx

Thanks!

Best regards,

Cosmo

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Cosmo,

SD = Normal Capacity

SDHC = High Capacity

SDXC = Extra Capacity

None of these have anything to do with speed class. On some cards speed class is marked by a number on the card itself, on others there is no marking at all. Anyway all SD cards are able to communicate at 24MHz. As for booting requirements, please check section 26.1.7.5 of the AM335X TRM.

0 Cosmo Yu over 12 years ago in reply to Biser Gatchev-XID

Intellectual 300 points

Hi Biser,

I remembered that AM335x doesn't have Micro SD card capacity limit on MMC0 port. So All kinds of capacity Micro SD card can be support by AM335x,right?

Would you pls help recommend one 8GB SanDisk Micro SD card to us? Which kind of speed class has the better performance on AM335x, 2, 4 or UHS Speed Class1?

Thanks a lot!

Best regards,

Cosmo

0 Biser Gatchev-XID over 12 years ago in reply to Cosmo Yu

TI__Guru**** 393215 points

Hi Cosmo,

The AM335X boots at up to 10MHz in 4-bit mode, which makes 20MB/s at most. The AM335X MMC interfaces support up to 192Mbit/sec (24MByte/sec) in High-Speed SD mode 4-bit data transfer. The SD card speed class mostly concerns write speed, which is considerably slower than read. My opinion is that you should choose a card that can be read at these speeds, which I think most cards will be capable of. As to size I think SDXC is not supported.

0 Steve Kipisz over 12 years ago in reply to Biser Gatchev-XID

TI__Genius 15510 points

Biser,

I think SDXC is supported. I thought I read it somewhere (sorry to be so vague). Earlier in the year we tested a 64GB SDXC card in an EVM and were able to read and write it.

Steve K.

0 Cosmo Yu over 12 years ago in reply to Biser Gatchev-XID

Intellectual 300 points

Hi Biser,

I totally understood. Thank your very much for your reply in patience!

Best regards,

Cosmo

0 Cosmo Yu over 12 years ago in reply to Steve Kipisz

Intellectual 300 points

Hi Steve,

Thanks for your information :)

Best regards,

Cosmo

0 Cosmo Yu over 12 years ago in reply to Biser Gatchev-XID

Intellectual 300 points

Hi BIser,

I have read the SD Card recommendations at below link:

http://processors.wiki.ti.com/index.php/TI-Android-ICS-4.0.3-DevKit-3.0.1_UserGuide#SD_Card_Recommendations

According to it, we should select SanDisk Micro SD card or SONY's. But we have problem to get their samples now. Pls help me confirm whether TI have tested SMART's Micro SD card or not.

According to below link, maybe we also can select Transcend's Micro SD card. Is that correct?

http://www.sakoman.com/OMAP/microsd-card-perfomance-test-results.html

Thanks!

Best regards,

Cosmo

0 Biser Gatchev-XID over 12 years ago in reply to Cosmo Yu

TI__Guru**** 393215 points

Hi Cosmo,

I work on hardware problems on the forums. The SD card recommendations are more of a software problem. I don't have information what cards have been tested and cannot recommend any manufacturer. My advice is that you perform your own tests on samples before you go buying large quantities.

0 Cosmo Yu over 12 years ago in reply to Biser Gatchev-XID

Intellectual 300 points

Hi Biser,

Yes, we'll buy some to test first. But we want to select the right parts from the beginning due to the tight schedule. Thank you all the same!

Best regards,

Cosmo

Processors

Processors forum

The Micro SD card speed class on AM335x