micro-SD card initialization using SPI interface

Question

I'm using a micro-SD card in an embedded design. The card is connected to a microcontroller using the SPI interface. It worked fine for all cards I've used before, but now my new card will not initialize. The card is a Transcend 2GB micro-SD card (TS2GUSD).

After sending the initial clock train to switch to SPI mode I do the following:

1) CMD0 (Argument 0, CRC 0x95) -> Response 0x01 -> OK

2) CMD8 (Argument 0x000001AA, CRC 0x87) -> Response 0x01 0x000001AA -> Means it's SDC V2+ card, the Voltage range 2.7V~3.6V is supported -> OK

Then I should send the ACMD41 command, but when sending the CMD55 (argument 0, CRC 0) that must precede CMD41, I get response 0x05 -> Illegal Command. I've also tried to send CMD1 (for MMC cards), but it gives a similar Illegal Command response. The code works fine with my Sandisk 2GB micro-SD card.

Does anyone have any idea?

Thanks,

-Ron-

Answer 1

It's normal, it's likely the internal charge-pump used to make erase voltage that takes longer than usual to be ready... you have to insist on the CMD55+ACMD41 combo until initialization finishes.

The CMD58 could also help you to check if you're supplying correct voltage levels (sometimes sockets have contact problems).

Answer 2

I seem to have found the issue. When I calculate the correct CRC for CMD55 and send that instead of a dummy CRC the command is accepted (result 0x01). If you look at the physical layer specification at sdcard.org (http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf) in section 7.2.2 is it explicitly said that: "The SPI interface is initialized in the CRC OFF mode in default." (except for commands CMD0 and CMD8). This doesn't seem to be the case with this series of Transcend cards, thus violating the specification. Also in case of CRC error the reply should be 0x09 instead of 0x05. I've tried to explicitly turn off CRC checking with CMD59 but that doesn't seem to help.

=> Calculating the correct CRC for (all?) commands makes the card work.

I'm in contact with Transcend support about this. If i learn something useful I'll you know here.

Note that I used other 2GB Transcend cards before, but they were made in Taiwan, while the new one is made in Korea (and seems to be a Samsung card (MMAGR02GUDCA)).

Answer 3

Hi, I think I have same problem with some Kingston MicroSD cards, can you post the Checksum used on the CMD55 ?

Also any comment on how to detect if the card does not support SPI mode at all? I heard SPI is not mandatory on microsd cards so I want a way to detect (and refuse the use) of a card if dont support SPI mode. I know if I run the initialization for those no-spi card it will fail, but I would like to detect in simple way and not wait till initialization fail.

Best Regards

• Francisco -

Answer 4

I'm using a Dane-Elec 1GB SDCard and I'm stuck with a similar, but not equal, problem. After the card receives the CMD0 command and enters in IDLE STATE I can't make it initialize. Almost every command is rejected with a ILLEGAL_COMMAND & IDLE_STATE. It rejects CMD1 and ACMD41. I tried CMD8 (in some webpages says that an ILLEGAL_COMMAND answering to that particular command may mean that the card is V1.X). I followed the CMD8 with a CMD58 to retrieve de OCR and once the card answered that the voltages were fine. I tried resetting the program but I keep getting 0xFF.

I can't initialize the card. I don't know if the messages need any special delay between the CS or the CLK.

Could anyone please help?

Thanks in advance

Cristian

Answer 5

when I send the CMD55 (argument 0, CRC 0) I get response 0x05 -> Illegal Command,and I send the CMD55 (argument 0, CRC 0x65),the response is still 0x05,Could anyone please help?