Re: SD card initialisation

On Mon, 1 Dec 2008 17:45:59 +0900, "Murray R. Van Luyn"
<NOSPAM@NOSPAM> wrote:

Thanks Peter.

It seems that I'm going to get a 0x01 response no matter how many times I
issue CMD0.

Also, it seems that I'm going to get an invalid response (0xFF) no matter
how many times I then issue CMD55.

Vexing!

Regards,
Murray R. Van Luyn.

"Peter Jakacki" <peterjakacki@xxxxxxxxx> wrote in message
news:dWMYk.2320$Et1.1805@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Murray R. Van Luyn wrote:
Hi,

I'm trying to initialise a 2GB Transcend SD card with an AT89C51AC2.

I send CMD0 and get a 0x01 response. It's initialising...

Then I send 10 CMD55 messages and get no valid response (0xFF) each time.
I don't know why I don't get a 0x01 response here until the card has
finished initialising?

Sound familiar to anyone?

You send CMD0 and that's fine but you need to send ACMD41 which is
CMD55+CMD41 combo. I don't put a limit on the number of times I do this
but depend upon a timeout instead. It depends upon the card.

*Peter*


Typically, you issue a CMD0 20 or 30 times to reset the card (I'm not
worrying about MMC cards here). Then you can follow w/ either a CMD8,
which distinguishes between SD +/- V2 cards, followed by the
CMD55/ACMD41 pair.

Question I have for you is. do you see the exact same behavior whether
a card is inserted or not? I have seen what looks like go_idle_state
(CMD0) succeed) followed by fails on CMD55, which turned out to be a
physical problem w/ the SD socket - broken switch or a piece of junk
wedged near the bottom.

Make sure the card is being electrically recognized before you start
worrying over the CMD returns.

Best, Tom
.

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