So I'm able to get my 18F2620 to read sectors off an MMC and SD card sing S=
PI
but when I try a high capacity SD card (SDHC) I can't get it to respond to
CMD0 to get it into SPI mode.  I'm able to read/use the SDHC card in my PC
but I'm guessing that it does not use SPI mode for this.

Reading the spec made me scratch my head as it seems to say that if the car=
d
does not feel like going into SPI mode it will not.=20

"The SD Card is powered up in the SD mode. It will enter SPI mode if the CS
signal is asserted
(negative) during the reception of the reset command (CMD0). If the card
recognizes that the SD mode
is required it will not respond to the command and remain in the SD mode. I=
f
SPI mode is required, the
card will switch to SPI and respond with the SPI mode R1 response.  The onl=
y
way to return to the SD mode is by entering the power."

I figure I need to get this resolved as it seems that the only cards you ca=
n
buy these days are SDHC.  I searched the web and just find people asking
questions about commands that are sent after GO_IDLE_STATE (CMD0).  I did
the 74 clocks with CS deasserted followed by a 100ms wait followed by
asserting CS low then hundreds of retries and wait for non 0xff responses
but the card just never drives the Dout line low.

The card I am using is a PNY SDHC 4 GB card (class 4).  Any suggestions
would be great.
--=20
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tp33000627p33000627.html
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--=20
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