6502_thing/main.py at master · raqbit/6502_thing · GitHub

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from assembler import assemble
from instructions import IncY, Jump, LoadA, LoadY, StoreA, NoOp, JumpToSub, ReturnFromSub, YtoA, PushY, PopY, StoreY
from label import Label
from modes import Addr
from rom import Rom

LBL_LOOP = Label("LOOP")

LBL_FN_OUT = Label("FN_OUT")

LBL_FOO = Label("FOO")


def main():
    # Memory Map

    # VIA: 0x6000 - 0x600F (repeating every 0xF addresses until 0x8000)
    # ROM: 0x8000 - 0xFFFF

    via = Addr(0x6000)

    via_portb = via
    via_ddrb = Addr(via + 2)

    rom_start = Addr(0x8000)
    rom_size = 0x8000

    init_vec = Addr(0xFFFC)

    code = [
        # Set PortB to all outputs
        LoadA(val=0xFF),
        StoreA(to=via_ddrb),

        # Init loop var
        LoadY(val=0x00),

        # Loop
        LBL_LOOP,
        YtoA,
        JumpToSub(LBL_FN_OUT),
        IncY,
        Jump(to=LBL_LOOP),

        LBL_FN_OUT,
        PushY,
        LoadY(val=0x00),
        StoreY(to=via_portb),
        NoOp,
        StoreA(to=via_portb),
        PopY,
        ReturnFromSub,
    ]

    code_ass = assemble(code, start=rom_start)

    filler = assemble([NoOp]) * (rom_size - len(code_ass))

    rom = Rom(size=rom_size, start=rom_start, init=code_ass + filler)

    # Write init vector
    rom[init_vec] = rom_start

    with open("rom.bin", "wb") as f:
        f.write(rom)


if __name__ == "__main__":
    main()