byter

Custom 8-bit CPU inspired by modified Nibbler arquitecture used in university course.

Characteristics

12-bit program counter.
16-bit width instructions.
4096 byte, 16-bit width ROM.
4096 byte, 8-bit width RAM.
16 8-bit work registers.
Call stack with depth of 8 addresses.
Register stack with depth of 8 values.
16 8-bit input ports.
16 8-bit output ports.
Carry and zero flag.
Also assembler compiler and simple vm included.

Instruction Set

Literals are loaded to register R14.
Value of RAM to read/write is through register R15.
When adding to program counter, lower nibble of register R13 is concatenated with register R12 for full 12-bits of address (PC += {R13[3:0], R12}).

Compiler

Simple compiler done in Haxe. Support for:

Comments
Labels for function calls
Variables
Hexadecimal, decimal and binary values.

VM

Simple vm in C for running compiled code, no interface with OS.

TODO

Redo compiler in C, with better asm syntax.
GUI for easier viewing of registers, pc, stacks, ports, etc in VM.
More detailed documentation.
Test in real FPGA.
Don't depend on apio for verilog?
Redo block diagram image for better visualizatoin without needing to be huge.