parse_nor_map.py

#!/usr/bin/python3

# Parses the ROM => NOR map of r4isdhc family carts

import struct, sys

canonical = (
'''N.B. mapping does not apply to 0x00 header read and 0x20 secure area read
Header [0x0, 0x200) => NOR [0x1F0000, 0x1F0200)
Header [0x200, 0x1000) => zeroes (presumably past 0x1000 too)
Secure area [0x4000, 0x8000) => NOR [0x1F4000, 0x1F8000)'''
)

NOR_SIZE = 0x200000 # 2M

def main():
    if len(sys.argv) < 2:
        print("usage: parse_nor_map.py <NOR file>")
        return
        
    with open(sys.argv[1], 'rb') as f:
        f.seek(0x40)
        mapping = f.read(0x100)

    rom_off = struct.unpack(">32I", mapping[:0x80])
    nor_off = struct.unpack(">32I", mapping[0x80:])
    del mapping

    for i in range(32):
        romlb = rom_off[i]
        romub = -1
        j = i+1
        while romub < romlb and j < 32:
            romub = rom_off[j]
            j += 1
        if i == 31 or romub < romlb:
            romlb = rom_off[i]
            norlb = nor_off[i] % NOR_SIZE
            print("ROM [0x{:X}, ... => NOR [0x{:X}, ...".format(romlb, norlb))
            break
        norlb = nor_off[i] % NOR_SIZE
        while romlb < romub:
            mapsize = min(romub - romlb, NOR_SIZE - norlb)
            print("ROM [0x{:X}, 0x{:X}) => NOR [0x{:X}, 0x{:X})".format(romlb, romlb+mapsize, norlb, norlb+mapsize))
            romlb += mapsize
            norlb = (norlb + mapsize) % NOR_SIZE
    
    print()
    print(canonical)

main()