measured colour output levels?

Discussion of development of software for any "obsolete" computer or video game system.
Opatus
Posts: 4
Joined: Sun Oct 18, 2020 4:29 am

Re: measured colour output levels?

Post by Opatus » Mon Oct 19, 2020 2:36 pm

Since you've already got everything tidily broken apart, I'd be casually curious what the inter-PPU bus (holding sprite data) looks like.
I'm not exactly sure what you mean by that. The PPU1 sends the color information and the priority of the sprite that's to be drawn for the current pixel. And then the PPU2 decides whether to draw the sprite or not, depending on the background and sprite priority.
I could make a test ROM that specifically puts two (palette+INIDISP) values that should be the same brightness (at least, closer than 1 part in 256).
Thank you, but I don't have an SD2SNES or similar to run custom code right now. I will just ice the idea for a while now, but it's still good to know.

lidnariq
Posts: 9855
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: measured colour output levels?

Post by lidnariq » Mon Oct 19, 2020 2:57 pm

Opatus wrote:
Mon Oct 19, 2020 2:36 pm
Since you've already got everything tidily broken apart, I'd be casually curious what the inter-PPU bus (holding sprite data) looks like.
The PPU1 sends the color information and the priority of the sprite that's to be drawn for the current pixel. And then the PPU2 decides whether to draw the sprite or not, depending on the background and sprite priority.
We know there's no delay? I guess that is succinct enough, then.

Opatus
Posts: 4
Joined: Sun Oct 18, 2020 4:29 am

Re: measured colour output levels?

Post by Opatus » Mon Oct 19, 2020 3:22 pm

I would assume it is delayed as the PPU2 will still have to do its magic on the sprite and background data. But I didn't measure the timing of the signals, nor does my CPLD has access to these signals.

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