Digital Design DDX 80T
This page was last modified 12:34, 21 May 2021 by Mars2000you.



The Digital Design DDX 80T is a special version of the DDX 80 cartridge as it combines access to the 80 column text mode on a MSX1 computer with an asynchronous RS-232C serial interface.

The video part is based on the Motorola 6845 CRTC, the controller used for the serial port is unknown.

It includes two 8kB ROMs, one with a specififc BIOS, one with character data. The 80 column mode is automatically initialised when booting the MSX with this cartridge inserted in a slot. However, a small button on the cartridge allows the interface to be disabled during startup.

Contrary to the Microsol VMX-80, the BIOS rom does not have its first part mirrored in the second part, because it includes more extra BASIC instructions - see DDX BASIC. The RS-232C instructions are not standard, they only allow to configure the UART and activate a terminal emulator (probably VT-52).

The mapping is done as follows:

  • 4000h - 5FFFh: ROM
  • 6000h - 6001h: access to the MC6845 registers
  • 7000h - 77FFh: MC6845 VRAM (2kB)

It comes with two video cables, one to connect to the MSX composite video output and the other to connect to the TV set or video monitor.

Brand Digital Design
Model DDX 80T
Year 1988
Region Brazil
Launch price
Package content
Emulation ROMs dump made, but only the BIOS rom has been decoded for using in emulators.



System Requirements

  • MSX1 computer with video composite output, one free slot cartridge