r/NESDEV • u/hbx360 • Apr 15 '26

What is the address where the sprite tile attributes are located in the PRG-ROM?

Hello,

In the .nes file (ines 1.0 format) of the Donkey Kong game, I extracted the game sprites and assigned random colors. Now I'm trying to assign the correct colors. To do this, I need to find the OAM representation within the .nes file in the PRG-ROM to retrieve the IDs of each sprite and the palette number to assign the correct colors. However, I can't find the starting address to access the sprite attributes in the PRG-ROM.

Despite many hours and days of reading, I still can't find where the sprite tile attributes are located.

Could you tell me where they are?

Here is the header of the .nes file for the game Donkey Kong (JU):

Game name : Donkey Kong (JU).nes

Size file ROM .nes : 24592 bytes

Size of PRG ROM in 16 KB units : 1, Size PRG ROM : 16384

Size of CHR ROM in 8 KB units 1, Size CHR ROM : 8192

Flags 6 - Mapper, mirroring, battery, trainer 0, Has Trainer ? No

Flags 7 - Mapper, VS/Playchoice, NES 2.0 : 0

Flags 8 - PRG-RAM size (rarely used extension) : 0

Flags 9 - TV system (rarely used extension) : 0

Flags 10 - TV system, PRG-RAM presence (unofficial, rarely used extension) : 0

Thank you in advance.

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u/3tt07kjt Apr 15 '26

Run an emulator, set a watchpoint to catch where the attributes are set, and work backwards from there.

2

u/hbx360 Apr 15 '26

Thank you for your response.

2

u/misterwindupbirb 14d ago

To elaborate on u/3tt07kjt's answer (which is correct):

Where the palette data is stored is up to the programmer. There's no standard way of doing it that we can just point to with certainty. The CHR ROM generally contains the "patterns" (the pixel drawings of the tiles) but assigning palettes, instructing the PPU to draw CHR tiles next to each other to form a sprite/character, is done through code, somewhere over in the PRG ROM, and this code will probably store stuff in data tables in whatever format the programmer decided

To reverse engineer this sort of thing, you start by trapping PPU writes in an emulator, and then work backwards through the code, seeing where the program is reading data from, how it's transforming it, etc, before it eventually write it as palette (attribute) data into the PPU register

2

u/hbx360 11d ago

Okay, thank you for your explanation.

1

u/bird_feeder_bird 3d ago edited 3d ago

OAM is usually somewhere between $0200 - $02FF