I am just trying to figure out how sprite manipulation is done in my favorite NES rom.
The point in the game I am looking at is after the ball has been snapped and the players are moving around.
I set a breakpoint for writes to $2003 and I see that 00 is written there each frame.
I do not see any writes to $2004.
I do see a write to $4014 every frame. So it appears to be accessing SPR-RAM via DMA.
At the breakpoint, the FCEUX debugger gives the line:
00:C153:8D 14 40 STA $4014 = #$FF
This means that $FF is in the accumulator, right?
So this should cause the 256th page to be written to the SPR, which would be FF00-FFFF?
I can't get it to break for any writes to this range. This would be mapped to the ROM?
Any ideas what is being done here? Is there some mirroring involved?
Thanks,
Fredrick
The point in the game I am looking at is after the ball has been snapped and the players are moving around.
I set a breakpoint for writes to $2003 and I see that 00 is written there each frame.
I do not see any writes to $2004.
I do see a write to $4014 every frame. So it appears to be accessing SPR-RAM via DMA.
At the breakpoint, the FCEUX debugger gives the line:
00:C153:8D 14 40 STA $4014 = #$FF
This means that $FF is in the accumulator, right?
So this should cause the 256th page to be written to the SPR, which would be FF00-FFFF?
I can't get it to break for any writes to this range. This would be mapped to the ROM?
Any ideas what is being done here? Is there some mirroring involved?
Thanks,
Fredrick