code = bytearray([
    0xa9, 0x42,
    0x8d, 0x00, 0x40,
    0xdb
    ])

rom = code + bytearray([0xEA] * (1024 * 32 - len(code)))

rom[0x7FFC] = 0x00
rom[0x7FFD] = 0x80

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