On Thu, Sep 29, 2011 at 2:46 PM, Herbert Graf <hkgraf@gmail.com> wrote:

> SPI mode on SD cards is likely nowhere near fast enough for your
> purposes.
>

Wikipedia says max 50 MHz via SPI for all but the oldest cards. I'll
benchmark it and see how it goes. I can use DMA with SPI, even better.


> CF in IDE mode is, but it's doubtful you'd be able to get enough
> bandwidth using a PIC and bit banging, you'd need a CPLD or FPGA (I've
> done it).
>

Yeah, that's why I'm staying away from CF.


> Note that both methods have variable write times that you'll have to
> account for. SD cards are known to write at steady rates for a good bit
> and then "hiccup" for a substantial amount of time, you'll have to
> account for that.
>

It'll be a buffered write. The buffers clear faster than the time it takes
to write, so hiccups will be okay. The DMA controller will handle the data
transfer from RAM to SPI.
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