| Re: [hatari-devel] Sync byte on Falcon |
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- To: "Roger Burrows" <anodyne@xxxxxxxxxxxx>
- Subject: Re: [hatari-devel] Sync byte on Falcon
- From: Thomas Huth <th.huth@xxxxxxxxx>
- Date: Sat, 9 Sep 2023 05:15:32 +0000
- Cc: hatari-devel@xxxxxxxxxxxxxxxxxxx
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Am Tue, 05 Sep 2023 20:31:56 -0400
schrieb "Roger Burrows" <anodyne@xxxxxxxxxxxx>:
> I always thought that bit 1 of the sync byte (0xff820a) on the Falcon had the
> same meaning as on the ST etc: a 1 bit means PAL (50Hz sync), a zero bit means
> NTSC (60Hz sync). But Hatari 2.3.0 disagrees: it always sets the 1 bit unless
> a monochrome monitor (71Hz sync) is connected.
>
> If that's really the way the hardware works, I'm extremely puzzled that Atari
> defined a PAL/NTSC bit in the video modes settable for RGB/TV, and that TOS4
> writes 0x02 to the sync byte (indicating 50Hz sync) for an RGB screen when the
> PAL/NTSC bit in the mode set to 1; and 0x00 to the sync byte (indicating 60Hz
> sync) for an RGB screen with the PAL/NTSC bit in the mode set to 0.
>
> This seems like a bug to me. If so, is it fixed in a later release?
This code has been added by Laurent more than 10 years ago:
https://git.tuxfamily.org/hatari/hatari.git/commit/?id=27f598b280618b6
I think this comes from "HE AUTHORITATIVE GUIDE TO THE FALCON VIDEO
HARDWARE BY AURA AND ANIMAL MINE", see e.g.:
https://bus-error.nokturnal.pl/dl124
It says:
$FFFF820A [R/W] _______0 .................................. SYNC-MODE
||
|+--Synchronisation [ 0:internal / 1:external ]
+---Vertical frequency [ Read-only bit ]
[ Monochrome monitor:0 / Colour monitor:1 ]
Is anyone with a Falcon able to reproduce this?
Thomas