MSX 512KB RAM and 2 ports serial cart
This repository contains the design for a MSX cartridge that features a 512KB RAM mapper and 2 ports PV16552 serial interface.
Both features are not dependent on hardware level so you can choose to only populate the RAM components on the right side or serial components on the left side of the cartridge if you don't need the other feature.
The 512KB RAM is implemented as a Gouget style mapper. It requires only a few easy obtainable components. This mapper doesn't self initialize and has no back annotation.
I have tested the RAM with a BEER232 interface on a MSX1 computer: if you boot with MSXDOS 2 then MSXDOS 2 will initialize the memory.
See also: https://www.msx.org/wiki/Memory_Mapper#Initialisation
The serial interface is implemented with a PV16552 which is basically 2x 16550. After reset the registers are initialized the same as a 16550.
The interface pins are TTL level and designed to be used with a ftdi serial to usb adapter.
Pin assignment left to right: GND,RTS,5V,RX,TX,CTS
Fit a jumper to JP1 or JP2 to provide +5V to the connected device (default not fitted) e.g. for usage with an ESP01 + adapter module.
Jumpers JP3 and JP4 determine the I/O port range: Connect the upper 2 pins for 0x80 to 0x8F Connect the lower 2 pins for 0x20 to 0x2F
The design of the cart was made so it is easy to build for anyone with basic soldering skills and knowledge of electronic circuits.
Schematics and Kicad project files are provided so you can make changes if you want to.
- Send the Gerbers ZIP file to your favorite PCB manufacturer for production
- Source the components in the BOM
- Populate the PCB with the components
- Set the jumpers
- Minimal test with a multi-meter the resistance between +5V and GND that there is no short circuit
- The cart should fit in a Konami type case with some cutouts (I have not tested this)
A new 1655x fossil driver v2 and tools are created that utilize the dual channel 16552 capabilities. It will also work with a single channel 16550 and requires MSX1 / MSXDOS 1 or higher.
The new fossil tools like xmodem are designed to be backward compatible if possible, meaning they may also work with the fossil driver v1.40 for vintage MSX RS232 peripherals.
Other MSX software that is designed to work with a 16550 UART most likely also works with the 16552 UART channel A.
- ✔️ Custom 16552 fossil driver to choose channel A or B and select I/O ports
- ✔️ Xmodem file exchange program (uses fossil driver)
- ✔️ VT52 serial console (uses fossil driver)
- ⬜ RS232C BASIC Extension BIOS (loaded in RAM)
- ⬜ VT100 serial console (server not client)
- ⬜ 80 columns support with the serial console for MSX1
- ⬜ UNAPI TCP/IP with ESP01 Wifi (use/adapt one of the existing solutions)
- ⬜ Use serial console with CP/M Plus
Build and use at your own risk! There is no warranty of any kind, either expressed or implied, that this cart will work with your MSX machine and/or software.
Copyright (C) 2024 H.J. Berends
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.