https://github.com/ikskuh/spu-mark-ii

CPU and home computer project
https://github.com/ikskuh/spu-mark-ii

assembler cpu spu-mark-ii zig ziglang

Last synced: about 1 month ago
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CPU and home computer project

• Host: GitHub
• URL: https://github.com/ikskuh/spu-mark-ii
• Owner: ikskuh
• License: mit
• Created: 2020-04-19T14:10:00.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2023-03-04T09:20:52.000Z (over 1 year ago)
• Last Synced: 2024-05-17T11:43:09.442Z (6 months ago)
• Topics: assembler, cpu, spu-mark-ii, zig, ziglang
• Language: VHDL
• Homepage: https://ashet.computer/
• Size: 29.2 MB
• Stars: 17
• Watchers: 3
• Forks: 1
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

README

        
# The SPU Mark II Project

A project that focuses on the development and improvement of the *SPU Mark II* instruction

set architecture.

Another focus is development and creation of a concrete implementation of the CPU in VHDL

as well as building a small "home computer" around an FPGA board similar to other computers

from the 80ies.

## SPU Mark II



The SPU Mark II is a 16 bit *RISC*ish cpu that uses the [stack machine](https://en.wikipedia.org/wiki/Stack_machine)

approach instead of a [register machine](https://en.wikipedia.org/wiki/Register_machine) approach.

The instrution set is documented in [documentation/isa.md](documentation/isa.md).

Short feature list:

- Highly flexible instruction set

- Conditional instructions instead of special conditional jumps or movs

- Optional hardware multiplication/division units (WIP)

- Optional interrupt handling (WIP)

To get a feel for the instruction set, here's a small example for a `void puts(char*str)` function:

```asm

puts:

	bpget ; function prologue

	spget

	bpset

	

	get 2 ; fetch arg 1

puts_loop:

	ld8 [i0:peek] [f:yes]

	[ex:nonzero] st8 0x4000     ; Use MMIO for text output

	[ex:nonzero] add 1

	[ex:nonzero] jmp puts_loop

	pop

	bpget ; function epilogue

	spset

	bpset

	ret

```

## Ashet Home Computer

The *Ashet Home Computer* is a computer built on top of the *SPU Mark II* cpu and

provides a small environment to use the cpu.

### Planned Features

- [MMU](documentation/specs/mmu.md)

- Video Output (either FBAS or VGA)

- Audio Output (signed 16 bit PCM)

- SD Card Storage

- Keyboard Interface

- Joystick Port (C64 style)

- UART interface

### Current Memory Map

Note that this memory map right now does not utilize the MMU, so bus width is 16 bit.

| Range               | Function           |

|---------------------|--------------------|

| `0x0000` … `0x3FFF` | Builtin ROM        |

| `0x4000` … `0x4FFF` | UART Interface     |

| `0x6000` … `0x60FF` | 256 byte fast RAM  |

| `0x6100` … `0x7FFF` | *Unmapped*         |

| `0x8000` … `0xFFFF` | 32k byte slow RAM  |