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August 16, 2006, 7:35 am
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Does anyone here understand how block addressing addressing works on SD
(secure digital) cards? I have a card that is FAT16.... and I can
initialized the card with my HC11, and can read 512 byte blocks of data
from it... however I can't understand how the addresses I'm using work.
It seems that no addresses will work untill address 0x200.... then only
multiples of 0x200 will work after that. This makes some sense I
guess, as 0x200 is 512 in decimal... so I guess I'm addressing blocks
of 512 bytes? But the confusion comes in when I try to look at my SD
card in HEX on my computer... the offsets don't seem to match up and
I'm unable to figure out how to get to a certain offset in the card
from the HC11. For instance, I know that a text file is stored
starting at 0x6A00 .
Anyone have some hints for me on this? I've never done any programming
with FAT's so maybe it's something universal to that and not specific
to SD cards.
Re: SD Addressing
Nevermind, I was looking at the card as a logical disk on my computer,
which makes 0x00 the start address of the logical drive, and not the
physical disk... I found a hex editor, WinHex that let's you look at
it as a pysical disk as well.
Take a look at this discussion for some really good information