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MMC storage — Parallax Forums

MMC storage

richaj45richaj45 Posts: 179
edited 2012-06-19 16:52 in Propeller 1
Hello:

Does someone know if the SD driver works with a MMC?

Thanks you.
rich

Comments

  • KyeKye Posts: 2,200
    edited 2012-06-19 14:18
    Yes, FSRW and the SD-MMC_FATEngine both work with MMC cards.
  • pedwardpedward Posts: 1,642
    edited 2012-06-19 14:52
    Kye's didn't work with my Sandisk 64MB MMC card. I've looked at the FSRW code and they don't do the 400Khz startup sequence required for MMC.
  • richaj45richaj45 Posts: 179
    edited 2012-06-19 14:59
    So what is the 400khz startup thing?

    That is can you point me to the MMC spec to educate me about the MMC protocol?

    rich
  • pedwardpedward Posts: 1,642
    edited 2012-06-19 15:24
    SD runs in SPI or qSPI mode, MMC runs in MMC or SPI mode, with the default being MMC.

    MMC does a 400Khz clock lock startup, then you send it a command to switch modes, from then on it acts much like SD. I don't have the info in front of me, but I have the docs at home.
  • KyeKye Posts: 2,200
    edited 2012-06-19 16:52
    I didn't say that my driver works with every MMC card. But, it does work for some.

    Back in the day, this was (and still is somewhat) and big issue for driver programmers. It is not true that all MMC cards work the same way and follow the protocol.

    Since the release of the SD 2.0 protocol all cards are now required to follow a strict set of standards. The original MMC and SD 1.0 protocols allowed a lot of *flexibility*.
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