SPI Microsd PCB layout - pull-up resistor

[Marco27293]

Hi,

I'm actually using a microsd (SDHC, 32GB) in SPI mode (using PIC18F device).
I have 51K pull-up resistors on MOSI, MISO, CS.
I connected DAT1 and DAT2 to GND.

Is this hw configuration correct ?
I read that also DAT1 and DAT2 should be connected to supply via pull-up resistors.

If I leave them connected to GND, could I experience any problems ?

Regards,

Marco

[Ttelmah]

Directly connecting any signal to ground, that may at times output, is
a sure way 'long term', to cause problems.
When running in one bit SPI mode, DAT1` and DAT2, can both output
signals. DAT2 can be the read/wait signal, and DAT1 can be an interrupt
output. It only takes a mode where these are enabled to occur, or these
to momentarily enable on a different make of card during the wake-up,
for a direct connection to result in disaster.
The specification says:
"It is the responsibility of the host designer to connect external
pullup resistors to all data lines even if only DAT0 is to be used".

[Marco27293]

Hi Ttelmah,

which specification do you refer ?

Could you give me a pdf or a link to it ?

Regards,

Marco

[Ttelmah]

www.sdcard.org

They charge for the full specification, but do a cut down version you should
be able to access. The quote is from version 3 of the full specification.

[Marco27293]

Could you give me a direct link for download ?

Or at least the full name of the required doc.

I did not find it...

[Ttelmah]

No. As I said, they charge for the full specification. There are cut down
versions from other people. I think National Semi, and Samsung both
do a simplified SD card specification sheet.

[jeremiah]

Simplified specifications based on a quick google search:
https://www.sdcard.org/downloads/pls/

[Ttelmah]

If he pulls section E1 from there, and looks at page 59, you have the
same message. "All hosts shall provide pull-up resistors on all data lines".