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SDHC on P2020DS, read block return null data

Question asked by Olivier Bluteau on Sep 28, 2012
Latest reply on Oct 10, 2012 by Olivier Bluteau

Hi,

 

I'm working with the P2020DS system. I use the linux driver for the eSDHC (cmd_mmc, mmc, fsl_esdhc....).

When I step in the init, the card is detected, the registers are read and the the registers content (OCR, CSD, CID...) appears to be as my SD specification is (TS2GSD150).

The configuration values are also set according to the SD capacity (4bits, voltage and frequency).

 

But as soon as I read the MBR (512 bytes @ block number 0), the only ouptut I get in my buffer is a null values expected for the MBR signature 0x55AA.

 

The only difference between the init and the read block memory, is the DMA and the SD card is in transfer mode instead of idle.

 

Can someone help me to figure out what I am missing?

 

Also, how the P2020 eSDHC peripheral handles the SD read access time? My SD card has a TAAC = 0x26 and NSAC = 0 which is 1.5ms.

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