This project is about achieving the basic knowledge how a computer really works by designing the hardware and all tooling/software on top of that.
This requires:
- Hardware modeled in Verilog
- An assembler for really low-level work which just saves us from writing 0's and 1's
- A UART bootloader which allows us to bootstrap the system
- A compiler to speed up software development
- A operating system
The idea comes from the outlining in 'From the transistor'
As everyone should be able to try this out without buying expensive hardware like a FPGA we will use the great Verilator to simulate our hardware model.
The available instructions and the binary format is defined here.
The relevant memory layout is visualized here. This layout defines where the bootloader and application code is placed in RAM, where the stack starts to grow and where hardware devices are mapped into memory.
The assembler language definition can be found here. Usage examples (*.asm files) can be found in the system-test.
A UART-bootloader is available, which allows to send arbitrary programs into RAM and execute them.
The hardware uses a IVT to handle interrupt handlers which must located at the beginning of the application code. See timer.asm or irq.asm for examples.
| Offset | Handler |
|---|---|
| 0x0 | Reset |
| 0x2 | UART1 |
| 0x4 | Timer1 |