Re: commodore 8032 vga / ports to monitor

From: Mia Magnusson <mia_at_plea.se>
Date: Sun, 25 Feb 2018 00:28:53 +0100
Message-ID: <20180225002853.000047a4@plea.se>
Den Sat, 24 Feb 2018 22:49:37 +0100 skrev didier derny
<didier@aida.org>:
> I guess that for my vga board, all I need to monitor
> 
> is the write in CRTC  (to reconfigure the screen emulated in the
> propeller)
> 
> and the write in $FFF0 to detect when the screen or I/O area are 
> shadowed by the 64k extension ?
> 
> 
> I've not seen anything else in PIA/VIA but I may have missed something
> 
> for me the 8032 it's quite old...

There is the "killer poke" that turns the VSYNC detect input to an
output. On the oldest PETs the hardware did drive hard enough that this
didn't matter but it disabled the timing logic halting the cpu when
accessing video ram while video were displayed. On newer machines it
messes up VSYNC output.

Don't know if there is any use emulating that behavior.

P.S. if you want some ideas for feature creep you might want to have a
look at the various hires addons for PETs :)

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Received on 2018-02-25 01:03:01

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