cbscpe wrote:
I have also thought of a prototype system. But rather having bricks I thought of having a base system with the CPU the RAM a fully programmable GLUE and a MCU assisted bootstrap loader and a small expansion bus.
My
L-Star project might be doing something in the direction you want to go, except there's no breadboard or glue logic.
It has a Propeller to bitbang the 6502 address bus and provide (PS/2) keyboard input, (monochrome) video output, a serial port (also used for downloading firmware). The Propeller also emulates ROM and RAM, but it's limited to 32K (including its own firmware) so it's possible to add an SRAM chip where the Propeller controls which addresses are used as ROM, which are RAM and which are neither.
I'm working on a kit (available soon on
Tindie) with a 128KB SRAM chip and an expansion port that includes all the signals (data bus, address bus, R/~W, clock, ~IRQ/~NMI/RDY/~SO/BE/~RESET, RAM enable, Propeller reset). I think my first expansion board will be a KIM-1/Elektor Junior board but it should be easy to implement other boards with programmable glue logic and a breadboard.
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===Jac