For interfacing that SD card, its datasheet doesn't really tell you much, similar to an 8051 datasheet. Like the 8051 it expects a basic knowledge of the SD specifications. Most require paid membership in the SD Card organization to access. The first thing you'll need though is the physical layer spec, which is available at their website:

http://www.sdcard.org/sdio/Simp...cation.PDF

There are lots of places to get the information on how to bit-bang an spi bus. For example, Atmel has apnotes detailing bit-banging an spi eeprom.

More difficult however will be once you get to where you can read and write the SD card at the physical layer, you'll want to do it at the logical layer, most likely involving FAT16/32...

That's more research you'll need to do.

Dennis