Re: SD card initialisation


"tporter" <tporter@xxxxxxxxx> wrote in message
news:hj3dj4lg1c9a62j1nor5tvfeefcr6kliu5@xxxxxxxxxx
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

Hi Tom,

Well the electrical interface is now 100% correct, thanks to your advice.
I'm still getting no further than CMD8. There's still no reply from the SD
card no matter how many times it's polled. As far as I'm concerned the
signals being issued to the SD card are okay. I'm stumped!

Regards,
Murray R. Van Luyn.


.

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