NES-MH

Cartridge Board

What Is It?

A chip on board cart.
74HC161
64K of PRG ROM
16K of CHR ROM

Note: this board has bus conflicts.

The Tech:

The HC161 acts as a latch. It latches D0 and D4. Writing anywhere in the 8000h- FFFFh range will set this latch using the above data lines. It is found only on the Super Mario Bros / Duck Hunt cartridge.

7  bit  0
---- ----
xxxP xxxC

The P bit selects the desired 32K PRG ROM bank.
The C bit selects the desired 8K CHR ROM bank.

Mirroring is hardwired on the cart.