SDHC questions

Feb 18, 2008 3 Replies
A

Hi there,



I need the SDHC spec cause I got to adapt existing embedded code to support the HC cards. neither google nor Sandisk helped. Any ideas where to get the spec from would be highly appreciated.



Do ordinary built in SD card reads in laptops support SDHC?



Is there anything out for cards beyond 32 GB ?



tia w.b.


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S

Google for SD Host Controller Standard Simplified Specification

Stephen

-- Stephen Pelc, snipped-for-privacy@mpeforth.com MicroProcessor Engineering Ltd - More Real, Less Time

133 Hill Lane, Southampton SO15 5AF, England tel: +44 (0)23 8063 1441, fax: +44 (0)23 8033 9691 web:
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P

I suspect that the OP is not interested in the Host Controller spec, but the High Capacity spec. I don't think that there is one though. It is part of the SD Spec version 2, which wasn't publicly available last time I looked. However, I have managed to figure this out myself. The basic differences are:

  • In the initialization at ACMD41 say you support SDHC (0x40000000).
  • In the CMD55 the reply should include SDHC support (0x40000000).
  • All sectors are 512 bytes and can't be changed by CMD16.
  • Offsets for reading and writing sectors are now sector numbers not bytes. So in theory you can access cards with 512x mory memory.
  • And the file system (as supplied) is FAT32.

I'm sure there is other stuff that I didn't need.

Peter

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S

What you need for HD is in the initialisation sequence diagrams.

However, as always reality intervenes when you test cards from several different suppliers.

Stephen

Stephen Pelc, stephenXXX@mpeforth.com MicroProcessor Engineering Ltd - More Real, Less Time 133 Hill Lane, Southampton SO15 5AF, England tel: +44 (0)23 8063 1441, fax: +44 (0)23 8033 9691 web: http://www.mpeforth.com - free VFX Forth downloads
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