Re: Re: PET video to VGA

Date: Thu, 3 Apr 2014 01:05:11 +0200 (CEST)
Message-ID: <30904744.247066.1396479911973.JavaMail.www@wsfrf1235>
After a significative break on the subject, I finally managed to have a "perfect" display to my VGA LCD screen using a GB8220 and a simple 74LS02.

The secret is on R03 that needs to have it's 4 high bit at least =2 (vSync width) ... but not zero.

Knowing that, my setting for R00 to R09 on the 8032 at 50Kz/15.63Khz (measured at osciliscope) for text mode are (in decimal) : 63,40,53,33,33,7,25,32,0,8.


Regards - Hervé

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Message du : 19/12/2013 17:53
De : "Rob Clarke " <>
A :
Copie à : 
Sujet : Re: PET video to VGA

 Here's my spreadsheet with all the timings from all common ROM's I could 
find plus the others that are on zimmers. You can use this to twiddle 
with the values and see the effect on the frequencies.

Anders is correct for the 80 column edit roms. For the 40 column ROM's 
the registers are at E7B1 and E7C3.


On 19/12/2013 13:21, Anders Carlsson wrote:
> Hervé wrote:
>> - What are registers values supposed to be OK ?
> Perhaps André:s site can help you?
> It seems to that changing the register R2 would move the image to 
> either left or right. The second page has actual register values, see 
> the ones for CS/A65 as those were tuned for a 50 Hz TV. André also has 
> links to the composite video adapters and mentions that the CRTC 
> values need to be changed in order to get them to work.
>> - Locations, in this hacked ROM, to patch to change those registers 
>> values ?
> A quick hunt with the xpet monitor suggests $E72A (lower case?) and 
> $E73C (upper case/graphics?), but I'm not entirely sure.
> Best regards
> Anders Carlsson
> Message was sent through the cbm-hackers mailing list

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Received on 2014-04-03 00:00:03

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