public void handler() {
            int A;
            UBytePtr rom = memory_region(REGION_CPU1);
            int diff = memory_region_length(REGION_CPU1) / 2;

            memory_set_opcode_base(0, new UBytePtr(rom, diff));

            for (A = 0; A < 0x10000; A++) {
                rom.write(A + diff, decode(rom.read(A), A));
            }
        }