Checksum.py

import os
import sys

romName = sys.argv[1]

checksum = 0

with open(romName, 'rb') as rom:
    while True:
        byte = rom.read(1)
        if len(byte) == 0:
            break
        checksum += byte[0]

    if romName.endswith('prom1.cpu'):
        rom.seek(0x1ff8, os.SEEK_SET)
        checksumBytes = rom.read(2)
        for byte in checksumBytes:
            checksum -= byte

        checksum += 0x01fe

    checksum %= 65536

    print(f'Checksum {hex(checksum)}')