MMC Flash Card Data Format

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I currently have the Atmel AT45DCB002 (2MB Flash Card) and it is partitioned to 4096 pages of main memory with 528 bytes per page.

Say I used a flash card reader/writer to throw a file into the flash card, how is the data stored? Is it encoded? Do different writer/readers store data differently? I know that for different type of files, the data will be stored differently, but what would be the best file type if I wanted to load in RAW Data?

Does anyone have documentation or info on how data is stored on an MMC Flash Card?

Basically, I want to be able to use a flash card reader/writer to put data into the flash card, and then use my processor to extract the information. Any ideas or help would be greatly appreciated!! Thanx!

- Aguilar

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A PC would typically store data to an MMC card in FAT16 data format. Although it's very detailed, here are some basics.

1. Data is stored in data units called Clusters. A "Cluster" may be composed of more than one sector (and usually is).
2. There are some areas that contain "housekeeping" information. These areas tell you were the data is located and how it's stored. These are the MBR (Master Boot Record), VBR (Volume Boot Record), FAT (File Allocation Table), Root Directory.
3. Data Clusters store (you guessed it) Data ! (actual file data).

The FAT tells you were the "pieces" of your file are stored. The memory card will be treated like any other drive. As files are added and deleted, "fragments" can occur. Therefore, data may not be stored in a linear manner. Data for the same file may scattered on the memory card. The FAT tells you where all of the pieces are.

Keep in mind that you do not HAVE to use FAT16. If you want, you can create your own storage format but keep in mind that your PC won't be able to read it.

Here is a link to a document which contains a lot of useful information on the MMC format.

http://www.sandisk.com/pdf/oem/P...

There is lots of information on web about FAT16; although, I have found some errors in some documents (beware).

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That's awesome... Thanx for the info! That's exactly what I needed.

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Hi

If you need source code for MMC and AVR just go to my web site at www.microsyl.com under led sign

Yours,
Sylvain Bissonnette

Yours truly,
Sylvain Bissonnette
www.microsyl.com