If the microSD card follows FAT32 file system (I do not know about other file systems), the audio file can be saved as any format of file. There is no special format for audio files. You dont have to address each byte.

The memory is classified as 512/1024/2048 bytes per sectors and 8 sectors per cluster. You have to save/retrieve data as a whole sector. You have to read boot sector to know the available memory, file entry table, free clusters, occupied clusters,etc.

I have done projects that uses microSD cards for data storage. My advice is "Study about file system".

Regards

Arun

Thank you so much #Arun K.

There are some data lines, supply pins, pin for clock and command are present in most memory cards. Depending upon the type of use (Reading, Writing, Formatting) the corresponding Pin is activated or deactivated.

The technique used for storing inside it is NAND flash memory technique. The data is stored in terms of 1 or 0 (Pulled up to Supply or Pulled down to ground when connected to a device). Along with this the data speed, storage capacity varies with different card types.

In Information Technology terminology you can go for the file system as answered by Arun K

A pinout details pdf is attached.

Thank you #sandeep mishra. I want to know how the address is allotted to each sector and how each sector is linked with another sector. because i want to interface 8051 micro-controller with microSD card. In that memory i want to save few audio files and i want to read them back. how can i do all this things with C programming ?, I can design an interfacing circuit with 8051.

I am not much comfortable on 8051 Programming. But you can easily get it from Rickey's World (Ajay Bhargav)

at http://www.8051projects.net/

Dear Anand,

You can interface the microSD card to native port (which is available in few high end microcontrollers) or SPI port. In your case, 8051 does not have SPI. (you have to try bit banking). If your try a microcontroller with SPI, then your work will be simple. your code length may decrease. My suggestion is to use AVR/ARM. It will be worth enough only if your SPI supports 1 Mbps or more. Else it will take long time to write/read the files.

There are a set of commands for reading/writing a microSD card.

Refer this link http://elm-chan.org/docs/mmc/mmc_e.html

This is the best tutorial for microSD I have ever seen.

In a FAT32 file system, every information about the mass storage device will be available in the Master Boot Record (MBR). The MBR will be in the first sector (first 512 bytes of the memory).

If you have any doubts, keep posting.

Regards,

Arun