NES-BNROM

Cartridge Board

What Is It?

A discrete logic Nintendo-made board.
Max 128K of PRG ROM, a 74161, and an 8K VRAM.
Note: this board has bus conflicts.

The Tech:

The LS161 acts as a latch. It latches D0 and D1. Writing anywhere in the 8000h- FFFFh range will set this latch using the above data lines.

7  bit  0
---- ----
xxxx xxBB

The B bits select a 32K PRG ROM page at 8000-FFFFh.


Mirroring is hardwired on the cart.