about the specification about MMC can be seen at **broken link removed**
this site is a MMC organization establish mmc specification.
you can also download a complete specification about MMC, but it is not free.
Hi,
You can use PsOC Chip (CY8C29xxx) for access Memory Card.
Cypress support new version 4.3 for SD, MMC,MiniSD module (8 nov. 2006) . www.cypress.com.