PM Graphics - DMA versus Reg & Priority

[Cybernoid]

Hmmm, I have a couple of questions for the gurus regarding PM graphics and priority.

 

While, messing with PM graphics and an emulator, I have noticed that if I disable the PM graphics DMA and write directly to the Graphics registers (0xd00d-0xd011) AND turn priority off (0xd01b = 0), then a few weird things happen.

 

In Antic E mode, Players 2 and 3 and all Missile colors are ORed with the Playfield colors. Player 0 and 1 seem to be on top (higher priority) of some of the Playfield colors, but not all of them. So Player 0 and 1 colors are ORed with some Playfield colors, but I haven't figured out which ones yet.

 

I haven't noticed this Playfield/PM color ORing with the DMA turned on.

 

I was wondering if anyone out there has messed with this and knows exactly what happens in this priority-0 mode. Does anyone know how Player/Playfield colors are ORed?

 

Thanks,

Chris

[Cybernoid]

Also, the reason why I am asking is I am working on a 8bit application and a game in my spare time, and it looks like in Antic E mode, you can have:

 

 

 

4 colors (one for each playfield)

plus 5 colors (one for each player/missile)

 

 

 

But, for each line, if you can OR each player with each playfield color, you can have a total of 20 colors per line, but dependent on player position. Is this right?

 

Thanks,

Chris

[emkay]

But, for each line, if you can OR each player with each playfield color, you can have a total of 20 colors per line, but dependent on player position.  Is this right?

 

 

It would be nice if it is so... but

 

You have only 2 players(plus missiles) that are usable with 2 playfield colors for this.

[Bryan]

I haven't noticed this Playfield/PM color ORing with the DMA turned on.

 

http://www.atariage.com/forums/viewtopic.p...r=asc&start=110

 

Here's a message I posted on this. I believe it happens whether DMA is on or off.

 

-Bry

[Cybernoid]

Ah, thanks. I seem to be getting different results with DMA off versus DMA on, but that could just be my stupidity in doing something wrong.

 

Oh well, thanks for all the information! I think I will mess with this a little more anyway...It does make some interest effects.

 

 

Cheers,

Chris