An exciting feature of the Chroma interface is its ability to add colour to the ZX81's display, with support for a palette of 15 colours and 2 colour modes. One mode provides an attributes file similar in concept to that of the Spectrum, giving maximum flexibility in creating a colour display but can only be used by new software developed to explicitly control it. The other mode allows colours to be assigned for each character in the character set, and then whenever a character is displayed it will be shown in its defined colours. The colour mappings are retained across a LOAD and so it is possible to load a game and for it to be displayed using the defined colours, i.e. existing games can be colourised!
The Chroma interface also provides the following facilities:
- An onboard 16K RAM pack.
- Additional 16K RAM that be mapped into the 48K-64K region, or the 8K-16K region.
- Support for a user definable character set within the RAM located in the 8K-16K region.
- Support for WRX graphics format, allowing true high resolution graphics.
- QS Character Board emulation, allowing a user definable character set and operating with the range of Quicksilva games that supported the original character board.
- A ROM cartridge socket that allows complete overriding of the ZX81 ROM, making it possible to run replacement operating systems or ROM enhancements, e.g. the Skywave FORTH ROM, the Comprocsys ASZMIC ROM, the dk'tronics and Kayde Graphics ROMs. The socket is compatible with my range of ZXC ROM cartridges, including the recently released ZXC4 that contains a 4MB FLASH ROM (opening the potential to store 100s of games on a single cartridge for instant loading and for recording these files directly from the ZX81).
- A Cursor joystick socket, with support for auto-fire joysticks.
- An RS232 socket, which could be useful for connecting to a printer, modem or a PC (a ROM cartridge program is already available to allow loading and saving via RS232 from a PC).
- Output of LOAD/SAVE sounds through the TV speaker(s).
- A set of configuration switches to allow each facility to be enabled / disabled, ensuring maximum compatibility with all existing hardware, e.g. ZXpand.
- A full width, gold plated rear expansion bus.
- A reset button.
- Transform the ZX81 into a ZX80, allowing it to run all ZX80 software!
- Load and save ZX81 programs via RS232 from a PC.
- Run the dk'tronics and Kayde Graphics ROMs.
- Upgrade an ZX81 with an edition 1 ROM to use the edition 2 ROM.
The Chroma interface can be used with all ZX81s irrespective of the ULA version they contain. It has been designed for compatibility with ZXpand and so it is possible to have a great quality picture and still load programs quickly from SD card!
Full details about the interface and the facilities it provides can be found at:
http://www.fruitcake.plus.com/Sinclair/ ... erface.htm