Tridora-CPU/README.md

Tridora

• the Tridora CPU and the Tridora System
• creating everything from the ground up (except soldering stuff)
• make it useful, but as simple as possible

Overview

• Homebrew CPU
• Verilog/FPGA SoC
• 32-bit word-oriented stack machine architecture
• has its own instruction set architecture, compatible with nothing
• additional IO controllers on FPGA: UART (serial console), SD-Card, VGA
• Pascal compiler written from zero
• CPU and compiler were designed together
• minimal operating system
• editor, compiler, assembler run natively
• so you can develop programs directly on the machine
• small: CPU has 760 lines of verilog, compiler ~9000 LoC
• Compiler written in Pascal and can compile itself
• Cross-compiler/-assembler can be compiled with FPC
• Compiler does its own Pascal dialect with some restrictions and some extensions
• Emulator available

Demo

• (Video hello world)
• (Video lines)
• (Screenshot mandelbrot)
• (Screenshot conway)
• (Screenshot image viewer)

Supported Boards

• Arty A7
• Nexys A7?

Pascal Language

• Wirth Pascal
• no function types/parameters
• arbitrary length strings (2GB)
• safe strings (runtime information about max/current size)
• tiny sets (machine word sized), that means no SET OF CHAR
• array literals with IN-operator, which can replace most uses of SET OF CHAR
• nested procedures with some limitations
• 32 bit software floating point with low precision (5-6 digits)
• break and exit statements, no continue yet
• static variable initialization for global variables
• non-standard file i/o (because the standard sucks, obl. XKCD reference)

Standard Library

• everything from Wirth Pascal
• some things from TP3.0
• some graphics functionality (to be expanded in the future)

Operating System

• not a real operating system, more of a program loader
• some assembly routines for I/O resident in memory
• one program image loaded at a time at a fixed address
• most parts of the operating system are contained in the program image
• file system is very primitive: only contiguous blocks, no subdirectories
• Simple shell reminiscent of TP3.0, edit, compile, run programs