This is my first digital voice recorder which is made using a mid range PIC with a total RAM of only 256 bytes. Generally people may say that we cannot access MMC/SD card using a microcontroller with a RAM < 512. I had seen such posts and comments in many electronics forums, sites etc. But now i could comment it is also possible to access MMC/SD using a uC with limited RAM but may have much limitations compared to uC with enough RAM.
Here, i used a PIC16F877A to access an MMC. MMC is interfaced to PIC16F877A via SPI. I didn't used any file system here. It writes the 8 bit digital data from ADC to the MMC using a multiple block write command. A single block consist of 512 bytes , also called as a sector.