# 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