raphnet.net banner

Modding a NES to run Unisystem VS arcade games (8/14)

Step 6: Additional wiring due to cartridge absence

1: The PPU memory /CE signal is usually controlled from an inverted A13 signal (inverted by U9, pins 5 and 6) and passes through the cartridge. This allows a cartridge to provide their own PPU memory and to disable the internal memory. Since we dont have any cartridge, contacts #58 (CHR /A13) must be connected to contact #57 (ciram /CE).

2: The A10 signal that goes to the PPU memory does not come directly from the PPU. It goes through the cartridge too. By connecting memory signal A10 to PPU A10 or A11, the cartridge can choose between horizontal and vertical mirroring. Since we have 4KB of memory, mirroring is not applicable. Just connect contact #62 (CHR A10) to contact #22 (CIRAM A10).

goto top

Next: Step 7: Button for coin insertion < 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 >

Any trademarks used on this site are the property of their respective owners.
Copyright © 2002-2021, Raphaël Assenat
Website coded withWebsite coded with vimLast update: January 7, 2020 (Tuesday)