CompactFlash (CF) cards are ideal for storage of large amounts of data, which is retained for years without the need for a backup supply voltage. In the wake of our CompactFlash Drive on IDE Bus (April 2002), we now present a similar circuit for microcontroller boards. Specific attention is given to the popular 89S8252 Flash Micro board which forms the hardware basis of our Microcontroller Basics course. The present CF interface was initially designed as an extension for the 89S8252 Flash Micro board published in the December 2001 issue of Elektor Electronics. The circuit may also be used in combination with other microcontroller systems provided you are able to make a suitable adapter between the CF interface and the extension connector on the system you have available.