NES-UOROM

Cartridge Board

What Is It?

A discrete logic Nintendo-made board.
Max 256K of PRG ROM, a 74161, 7432, and an 8K VRAM.
Note: this board has bus conflicts.

The Tech:

The LS161 acts as a latch. It latches D0, D1, D2, and D3. Writing anywhere in the 8000h- FFFFh range will set this latch using the above data lines.

The PRG space is broken up into two 16K banks. The upper bank is hardwired to the last PRG ROM page. The first 16K bank is selectable.

7  bit  0
---- ----
xxxx BBBB

The B bits select a 16K PRG ROM page at 8000-BFFFh.

Mirroring is hardwired on the cart.