[atari7800] Re: set WM every frame?
- From: "Greg DeMent" <gregdement@xxxxxxxxx>
- To: atari7800@xxxxxxxxxxxxx
- Date: Tue, 09 Nov 2004 02:48:30 -0800
----- Original Message -----
From: "Eric Ball" <ek-ball@xxxxxxxxxx>
To: <atari7800@xxxxxxxxxxxxx>
Subject: [atari7800] Re: Odp: Re: Aw: Re: Mode 160B don't works for me...
Date: Wed, 3 Nov 2004 18:35:58 -0500
>
>
> The Write Mode bit needs to be set at least once per frame, and it affects
> all sprites after it in the display list. So even if indirect sprites are
> not required, there needs to be at least on 5 byte header in the display
> list to set the Write Mode. I typically point one of the offscreen DLs to a
> display list which contains the one 5 byte header which describes a 1 byte
> direct sprite positioned offscreen.
>
From pg.9 in the Software Guide, it says:
"WRITE MODE is specified via the WM bit of an extended (5 byte) header, as
described above. READ MODE is specified via the CTRL register. Both of these
specifications will remain in effect until respecified. WRITE MODE is not
initialized by MARIA on power-up, and must be initialized by the cartridge
before any display occurs."
The way I read this, it seems to imply that you only have to set the Write Mode
once. Are you sure it has to be reasserted for each frame?
I've been using a procedure that sets the Write Mode at startup, but then
removes that header later. I can't test on real hardware though, so I haven't
confirmed that it works.
--
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