[Coco] FW: CoCo2 lower graphics
mikep at twcny.rr.com
Mon Jun 20 19:12:53 EDT 2016
That was it. Swapping out the SAM chip did the trick. I had to replace the
SN74LS785N with a SN74LS783 chip. But so far everything seems to be running
as it should. Thank you a bunch for the quick responses.
Date: Sun, 19 Jun 2016 07:33:11 +0100
From: Ciaran Anscomb <cocomalt at 6809.org.uk <mailto:cocomalt at 6809.org.uk> >
To: coco at maltedmedia.com <mailto:coco at maltedmedia.com>
Subject: Re: [Coco] FW: CoCo2 lower graphics
Message-ID: <17321.1466317991 at candle.6809.org.uk
<mailto:17321.1466317991 at candle.6809.org.uk> >
Content-Type: text/plain; charset="us-ascii"
"Michael Pittsley" wrote:
> I was unable to send this to the group due to the attachments being too
> large. Any additional assistance you could give would be grateful.
Hope you don't mind, I'll reply to the list, and have uploaded the jpegs
> I'm not really sure how to respond to these messages on here. I hope
> I have it right. Anyhow. Running screen0,1 goto 10 doesn't do much.
> From the TV I have the CoCo connected to, it presents an orange line
> that runs up and down the screen until I press break. Attached see
> the screen shots or what I am talking about the lower / bottom half the
graphics not working.
So to me the Frogger shot looks like a low-res mode is being presented as
hi-res. The VDG itself doesn't do this, it's the SAM that handles the
addressing, so if possible I'd try replacing that chip (6883,
SN74LS783/5) - everything else the SAM does looks like it's working so I'd
guess at some internal fault just limited to the video address counters or
- Michael Pittsley
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