DragonMMC SDCard

From The Dragon Archive

DragonMMC is a mass storage device for the Dragon 32, Dragon 64 and Tandy CoCo 1 or 2 that provides fast access to files stored on an MMC or Secure Digital format card. The board is sized so that it will fit in the same case as the DragonDOS cartridge.

The main facilities provided by DragonMMC

  • Ability to load and save files direct to the card.
  • Ability to load and save at high speed from emulator tape images (.CAS).
  • Emulation of Dragon DOS (Dragon) or RSDOS (CoCo) disk system through disk image files (.DSK/.VDK).
  • Ability to organize files into a hierarchical structure using directories.
  • Due to using the FAT or FAT32 filesystem on the card, ease of exchanging files with emulators running on a more modern computer.
  • Ability to “stream” tapes from real cassettes and generate emulator files (.CAS) from them.
  • “Snapshot” facility allowing the user to take an image of active memory and save it onto the card for loading later.
  • Game cartridges images (.ROM) can be loaded from the card into the on-board RAM and executed as if the cartridge was directly connected to the machine.
  • Auto detects whether it is running on a Dragon or CoCo at start up and uses the correct ROM image for that machine.
  • Easily upgradable from the Dragon/CoCo as new firmware is released.
  • Battery backed clock to ensure that files created have the correct dates /times and the clock is accessible from BASIC.
  • BASIC commands to allow DragonMMC integration into your own programs.
  • Retokenization command to allow exchange between Dragon & CoCo basics.

Supported platforms

  • Dragon 32
  • Dragon 64
  • DraCo 64
  • Tandy CoCo 1
  • Tandy CoCo 2


  1. As the DMMC relies on the cartridge/expansion memory area, it is only (currently) compatible in 32K mode.
  2. Only tested with Tandy CoCo machines that have at least 32K, since the interface can run with DOS disabled, it should run on a machine with only 16K. However, operation on a CoCo REQUIRES extended Colour basic.
  3. There is no hardware reason why the board could not be made to work on the CoCo 3, however this currently will not work due to an incompatibility between the Firmware on the CoCo 3 and the DragonMMC.
  4. The board may also work with the other CoCo clones that exist as long as they have the same cartridge port specification, it has however not been tested.


Version 1.25 betatest

Minor cleanups in the implementation of the CPLD code.

Added ability to use DragonMMC rom socket to update DragonDiag rom.

Firmware : Firmware 1.25 beta

Version 1.20

This updates the AVR and Dragon firmware to the latest version. There are no changes from 1.00 for the CPLD.

This version has preliminary work needed to be able to boot Flex & NitrOS9 along with a fix to the disk handling affecting CoCo disk images.

Firmware: Firmware 1.20

Flex boot utilities : Flexboot utilities 1.20

Documentaion : Documentation 1.20

Version 1.10

Updated release 2018-06-18, changelog here : Changelog 1.10

This updates the AVR and Dragon firmware to the latest version. There are no changes from 1.00 for the CPLD.

Firmware: Firmware 1.10

Documentaion : Documentation 1.10

Explorer : Explorer 1.10

Version 1.00

Initial releases of firmware and documentation 2017-09-12.

Firmware: Firmware 1.00

Documentaion : Documentation 1.00

Explorer : Explorer 1.00