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In connecting the ColorVDU to different monitors, do remember that
EGA and CGA require different timing parameters.<br>
<br>
The following is copied from: Wilton, Richard, <i>Programmer's
Guide to PC and PS/2 Video Systems</i>, Microsoft Press, 1987.
ISBN 1-55615-103-9.<br>
<br>
Figure 2-7, p. 24:<br>
<br>
mode dot clock (oscillator) hor. scan
rate vert. scan rate<br>
EGA 640x350 16.257mhz
21850 60<br>
EGA 720x350 16.257mhz
18432 50<br>
<br>
CGA 640x200 14.318mhz
15750 60<br>
<br>
VGA 720x400 28.322mhz
31500 70<br>
VGA 640x480 25.175mhz
31500 60<br>
<br>
Ideally, the ColorVDU would use VGA output, but the 8563 chip has a
maximum input frequency of 16mhz. This leads to the compromise on
the 15-pin HD-DB connector of EGA scan rates using 720x350 mode
(9-bit characters). The timing parameters are hard coded into the
setup routines in the SBC-188 BIOS, and, I believe, the RomWBW BIOS.<br>
<br>
To use the CGA output, changes the use of the ColorVDU entirely,
both in hardware and software. To achieve the exact IBM video
timings, both the oscillator can (h/w) and the CRTC timing
parameters (s/w) need to be changed.<br>
<br>
Dan originally obtained his output using a CGA-to-VGA converter.
His earliest test programs are in the file, "CVDU Test
Programs.zip," on the Wiki. I would suggest contacting him directly
on using CGA output from this board.<br>
<br>
--John<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
On 04/25/2014 06:18 AM, Dan Werner wrote:
<blockquote
cite="mid:CAMx0vHZy5C0aqxm-uQV+nc-oitW_9=kZaiwn6FimfT+tZ30QOg-JsoAwUIsXosN+***@public.gmane.org"
type="cite">
<div dir="ltr">
<div>What ROM image are you using?  It sounds like the
hardware is working ok (that is the normal behavior)-- and the
monitor should be fine (that is the same type of monitor that
I use).</div>
<div>Â </div>
<div>
Dan</div>
<div>Â </div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Fri, Apr 25, 2014 at 2:18 AM, Frank
Rasmussen <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:frankrasmussen2-***@public.gmane.org" target="_blank">frankrasmussen2-***@public.gmane.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div dir="ltr">
<div>Hi All</div>
<div><br>
</div>
<div><br>
</div>
<div>I hope that someone can help me with my problem.</div>
<div><br>
</div>
<div>I have build the CVDU Card , rev. 1.0-005 , made the
mods as described in docs. I have build the 10 pin
to CGA cable and are using an old CRT monitor which I
normally use for my C-128.</div>
<div><br>
</div>
<div>For the rom image I have choosen one of the
readybuilt ones - N8VEM_diskio3+cvdu.rom.</div>
<div><br>
</div>
<div>When powering up the system - I get a lot of garbage
on the CRT and then after a second or so, a blinking
cursor then nothing more happens on the CRT.</div>
<div><br>
</div>
<div>On the tty term i see the normal bootup process, CVDU
enabled and 64K ram found - which is correct as I use
4464 IC's.</div>
<div><br>
</div>
<div><br>
</div>
<div>What can be wrong - did I forget anything ?</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Best regards</div>
<span class="HOEnZb"><font color="#888888">
<div>Frank</div>
</font></span></div>
<span class="HOEnZb"><font color="#888888">
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