Where should I discuss SD/MMC FAT issues? - Page 2


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  1. #32
    Join Date
    Mar 2008
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    Texas, USA
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    Something is wrong with my Tcy counter. It must be rolling over. I didn't make provisions for it rolling over because I couldn't imagin it taking more than 65K Tcy to move the data off the MMC and onto the F-RAM. I guess I was wrong... very wrong.

    Best condition Tcy's to move data:

    gosub to MMC read - 2Tcy

    get byte - 24Tcy (3Tcy per bit)

    return - 2Tcy

    gosub to write F-RAM - 2Tcy

    write F-RAM - 117Tcy (13Tcy per bit (min. clock delay 5Tcy), 9 bits w/ack)

    Ack overhead - 9Tcy if tested, 3Tcy if blind read

    return - 2Tcy

    total for single byte loops - 158Tcy

    repeat 512 times - 80,896Tcy

    I must be moving data WAY slower than I thought. Time to detect TMR1 rollover and see what it really is.
    Last edited by JD123; - 22nd March 2008 at 17:01. Reason: corrected F-RAM Tcy
    No, I'm not Superman, but I did stay at a Holiday Inn Express last night!

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