Hi
A quick update on the progress of this S-100 Utility board. My goal is to create a board that accomplishes two goals:
1. provide complete MSX hardware compatibility when paired with the S-100 Z80 CPU board and S-100 VDP (to be released soon)
2. provide a general purpose SRAM + IO board that can be used to bootstrap a basic S-100 system.
At the moment, working with Dan and Alexandre, I have a prototype ready for review. Basically this board is the guts of an MSX computer minus the TMS9918 (V9938), AY-3-8910, and CPU. It has 32KB boot ROM and 32KB SRAM in "slot 0", an expansion cartridge port for "slot 1", 64KB SRAM for "slot 2", and an expansion port for "slot 3". It uses an 8255 PPI for a really interesting memory bank switching controller and Matrix ASCII keyboard interface.
The board provides general purpose IO including: 16550 UART, Centronics-like (not PC compatible) parallel port, Matrix ASCII keyboard interface, cassette control interface, and MSX Cartridge and Expansion port slots.
Please note this design can be completely separate from MSX and still be useful. For instance, it could boot from the ROM and load CP/M into a 64KB SRAM memory similar to how the N8VEM SBC V2 does now. The MSX compatibility is completely optional and the board would make for a useful 8-bit ROM, RAM, serial port, and parallel port board on its own.
Ideally we could make this a group project like the S-100 VDP board. After three rounds of prototype boards, thanks to Leon and John, the board is approaching a useful video and sound board. The S-100 Utility board would make a great complementary board and I think it would be worthwhile.
I know we've discussed and even attempted design of a basic 8 bit memory and IO board in the past but so far nothings come of it. Maybe this is our chance?
Please let me know if you would be interested in participating. I have a preliminary schematic and PCB layout already. It sorely needs review by a knowledgeable eye to ensure the logic is right for S-100 proper operation. I will post a version on the Wiki if it will help.
Thanks and have a nice day!
Andrew Lynch