The monitors are monochrome, and the following gives some info about them:

http://en.wikipedia.org/wiki/Hercules_Graphics_Card

720=D7350 resolution
Uses 5V TTL electrical signaling.
Horizontal frequency 18.425 +/-0.500 kHz, Vertical frequency 50 Hz.
Pinout: http://pinouts.ru/Video/MDA_pinout.shtml

You should be able to display video with that information, the only
thing remaining is to find front porch, back porch, and perhaps fiddle
with the sync pulse widths.

-Adam

On 1/3/08, Mauricio Giovagnini <maugiovagnini@yahoo.com.ar> wrote:
> Hi, I'm trying to do something with some old monitors I have
> around.
>
> I have 2 HGC (Old Hercules PC board) monochrome monitors and
> a couple of VGA ones and I would like to know how to deal
> with them with a microcontroller.
>
> I've seen around some open circuits to deal with them with
> FPGAs and or Logic Gates.  I've also read about the MC6545
> and similar circuits.
>
> What I would like to know or to read about is the timings
> and how they should be handled in order to make them work.
> I've read here and there without any clear scheme or timing
> graph.  Can anyone point me a link, book, pdf or something
> related in this direction?
>
> I know I need a fast device, I think a dspic 33F will be
> enough for the Hercules Interface and for a VGA in 320x200 mode.
>
> My goal is to replace the monocrhome Graphic LCDs a more
> specific and 'bigger' screen.
>
> Thanks in advance
> Mauricio
>
>
> --
> ------------------------------
> Mauricio Giovagnini (Maunix)
> www.maunix.com.ar
> Cordoba, Arg.
> LinkedIn Profile: http://www.linkedin.com/in/mgiovagnini
> --
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