The MMC2IEC device

It has always been tricky to transfer data between a PC and a Commodore 64. As the old machine lacks any even remotely modern interfaces, tricks of some sort are always required to do the transfer. The MMC2IEC device can be seen as yet another one of these tricks, but it does so much more.


The MMC2IEC device tries to simulate a 1541 disk drive connected to the C64 using the IEC bus and accessing data from a SD/MMC flash memory card. The MMC2IEC is both greatly limited and greatly extended in features when comparing to the original 1541:

Features: (as of v0.7)


Background and credits

The idea of transfering data to the C64 from a flash media was conceived long ago as I did an university project. In cooperation with other students we created a data logger interfacing a SD-card using an AVR. The SD-card data access and FAT driver modules were created back then and they were thoroughly tested. The FAT driver is not completely my own invention, it is a partial rewrite of work done by Angelo Bannack and Giordano Bruno Wolaniuk who used work done by Pascal Stang. See fat.c for details.

At some point I discovered Jan Derogee's 1541-III device which was a major inspiration. Before that I considered creating a C64 datasette simulator, but the 1541-III made me realise that it was possible to simulate a 1541.

The MMC2IEC project thus started as an attempt to port Derogee's 1541-III from PIC to the Atmel AVR architecture such that I could combine it with my FAT and SD-card modules. Soon enough I gave up the porting and implemented the IEC and 1541 simulation from scratch, but it would have been impossible without referring to Derogee's project all the time.

At a later point I realised that the MMC2IEC was perfectly suited for embedding in a C64-DTV mod. And so far I have only tested the MMC2IEC on a DTV in conjunction with my Wooden DTV mod.

This project is open source under the GPL license.


By Lars Ole Pontoppidan

Feb 2007

Last update: May 2007


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