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BF525 - SD Card over ASYNC/EBIU bus - Note EE-335

Question asked by nick0mg on May 27, 2012
Latest reply on Jul 3, 2012 by Nabeel

Hello, I am looking for some help or advice on interfacing an SD Card using the ASYNC bus as described in app note EE-335, Interface III. The board set-up is BF525 plus 32MB SDRAM and an SD Card connected to the ASYNC bus as described in EE-335, figure 19.


The problem I am seeing is that when code is run from external SDRAM the SD Card doesn't always respond and often get CRC read errors. Running the same code from internal SRAM I don't see any issues, the SD Card performs correctly. Unfortunately my application is too large to run from SRAM - that build is just running the SD card drivers.


With my full application build I tried placing the SD driver files into internal SRAM, this also hit CRC read errors. But have found that if I move all the bsz $OBJECTS and $LIBRARIES into SRAM the CRC errors reduce. Not sure why?


It looks like either the linker map is incorrect or some odd interaction between SDRAM and the SD Card. Any thoughts welcome? Attached are the SRAM and SDRAM linker files.


There is no other code running at the same time as the SD driver and I have check the SDRAM set up and appears  correct,