SD card/MMC card electrical compatability

[Mark R]

I'm trying to design a device based around a simple 8-bit MCU, which will log data to a memory card.

Currently, I plan to write data to an MMC card in SPI mode. As 128 MB may not be sufficient, I was wondering about the compatability of SD cards.

Do they support SPI mode, and the MMC command set? I can't find any datasheets that don't cost thousands of $.

 

[Shalmanese]

Hmm... I dont know how useful this is but every SD card reader I know of can read MMC Cards. I think the only main difference between the two is that SD has some DRM stuff.

 

[tdowning]

AFAIK, SD is simply a MMC with a special electronic serial number, (Think PIII) that is used, as mentioned above for Digital restriction management.