Re: SD Card Controller
@dkk
Sorry about the delay. Was a little but busy these past few days.
The latest spec is version 3.00 (Includes SDXC). The specification I was referring to in my earlier post is Version 2.0 (includes SDHC). This is the latest version that is shared by the SD Card association with the public. Using info found on these docs, you can only build a SD Card host (not an SDHC or SDXC host). as for microSD .. I haven't researched these.
Although the full ver 2.00 spec should include all the info on the SDHC card, the simplified spec only contains some info; From what I've got,
+ The block size used for data transfer in version 1 could be changed between 1 - 512. In version 2 this has been fixed to 512 bytes.
+ In ver 1 address fields in CMD17,18,25,24 specified the byte address. In ver 2 the block address is specified.
+ Ver 1 hosts had to clock out signals on the
cmd and
data pins at the neg edge. Maximum clock was 25 MHz. I
"think" in ver 2 signals are clocked out the the pos edge and max clock freq is 50 MHz (I can't be sure though)
+ Some register structures are different in the two versions (I forget which).
I
"think" in ver 3, the
data signal is clocked out on both the rising and falling edge of the clock. This is just a guess I made, based on the MMC spec and some other data sheets I've seen.
The only way to verify these doubts is to actually write to a real SDHC, SDXC card and see. Will let you know If I have any progress
Other than that, I don' know of any difference in the physical interface. Maybe someone more knowledgeable could help out.
Hope this was of some use
btw ... At this point, I'm still not sure if we can sell the SD card host as SD ver 2.00/ver 3.00 complaint host without a valid license from the SD card association. Any ideas on that ?
@samuraign
I'm currently using the SD card model from open cores. I've patched it to accept multi-block commands as well. But it would be better to use something like the model from Denali.
Do you have any idea on how to obtain the model? The cost? Are you using it right now? I read somewhere that Denali will only sell the model if we have a valid SD card license. Is this true?
Would be grateful for any pointers.
Regards
Nuwan