The SD card can be interfaed

[dagakshay]

The SD card can be interfaed by using SPI

 

here is the link for SPI in ATmega16 tutorials:

http://www.engineersgarage.com/embedded/avr-microcontroller-projects/spi-serial-peripheral-interface-tutorial-circuit

 

also see external EEPROM interfacing link(given on this site) it will help you in understand the memory architecture….