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.