SD/MMC Card without CS line?

mbro131 · Joined: 22 May 2006 Posts: 9

Is it possible to perform any operations on an SD/MMC card with the CS line tied low on the card (SPI mode)?

I threw together a design and assumed (yes.. i know) that the CS line was only used for selecting which peripheral was active and as I am only using a single card I couldn't see the need for it.

Now it seems that the falling edge of the CS line is used by the SD card prior to bus transactions.

If anyone knows whether this is correct or not it would be appreciated.. I would like to avoid modifying my circuit if possible.

Regards

Matt

Guest · Posted: Tue May 30, 2006 11:26 pm

i think you are fried, you can´t even init the card without changing the state of this line.

mbro131 · Joined: 22 May 2006 Posts: 9

Yer I suspected as much.. I guess my circuit just got uglier..

Lesson: Don't Assume!

Matt