ASCII-X FlashROM cartridge
Copyright 2024 Laurens Holst
Project information
Open and low-cost FlashROM cartridge design for large cartridge games.
- Author: Laurens Holst laurens@grauw.nl
- Site: https://www.grauw.nl/projects/ascii-x/
- Flash tool: https://www.grauw.nl/projects/ascii-x-flash/
- Source: (coming soon)
- Documentation: ASCII16-X specification
- Support: https://www.msx.org/forum/msx-talk/development/ascii-x-flashrom-cartridge
- License: MIT
The ASCII16-X cartridge for MSX is an extension to the common ASCII16 mapper. It provides extended memory capacity, FlashROM memory which allows for persisting save games, mirroring of pages and bank select registers across the entire address space, and is backwards compatible with existing software.
The primary goal of this project is to provide the MSX community with open hardware implementations of ASCII mappers with these extended capabilities, using only commonly available parts, and aimed at optimising manufacturing simplicity and cost. As such, this project also contains actual cartridge hardware implementations built with plain logic ICs.
The following cartridge designs are currently available:
These designs are made using KiCad 8.0.9. Their dimensions target the Overrich cartridge cases. Board width is kept under 10 cm to allow for cheap PCB fabrication. The surface mount components are also all on a single side for cheaper PCB assembly, as well as simplified hand-soldering using a stencil.
Media
Cartridge hardware designs
ASCII16-X Mapper Extra Large (XL) 8 MB
This design is suitable for large ROM cartridges of either 4 MB or 8 MB.
Since FlashROMs above 2 MB are only available in 3.3V versions, it requires circuitry for voltage translation between the 5V MSX bus and the 3.3V FlashROM.
The design utilises an Infineon 8 MB FlashROM which is currently the most economical choice, though it also supports smaller capacities. The board has 3 logic ICs for the mapper logic, and 5 additional logic ICs as well as an LDO for the voltage level translation.
Specifications
ASCII16-X
- FlashROM memory with commands for per-sector erasing and programming.
- Extended addressable capacity up to 64 MB (design provided for 8 MB).
- Two 16K mapper pages, mirrored to the full address range.
- Two bank selection registers accessible in all pages.
- Mostly backwards compatible with ASCII16.
See ASCII16-X specification for documentation.