It has been a long time since my last CPU project, which focused on a very simple 8 bit CPU. Nothing groundbreaking, just a very simple variation of an accumulator machine.
This time I have set out a different, more ambitious goal. I have wanted to create still something simple, but original unconventional architecture, which is still useful.
I had considered to target a CPU optimized for logical programming, but finally I have decided on a CPU with an instruction set and architecture, which natively supports functional programming.
A tagged architecture is selected. Basically, this means that each unit of information carries its own type information. A special instruction set will be carefully selected, which would be most useful to support creation of functional programs in assembly or even in machine code. The whole design will be very simple, yet powerful enough to perform arbitrary complex computations (in theory) to be Turing-complete.
It will have
- no PC;
- no SP or stack;
- no conventional user readable flags;
- no user readable registers (not even an accumulator in the conventional sense);
- no branching/jumping instructions;
- no I/O operations
So, what is what we have?
- 7 bit literals (yep, not mispelt!);
- 3 built-in,
- 32 user-definable functions;
- ROM – to store functions (256 bytes);
- RAM – to evaluate expressions (256 bytes);
- 8 bit data bus;
- 8/9 bit address bus.