Jens Dyekjfr Madsen wrote:
>
> Oyvind Kaurstad wrote:
> >
> > Hi, all.
> >
> > I'm planning to make a video capturing device using a PIC
> > and a PC parallell port.
> >
> > What I have is a composite 1 V p-p video signal (monochrome, no color
 bursts)
> > (The signal is CCIR, 50 Hz field frequency, interlaced)
> >
> > I have a lot of ideas on this, but I would appreciate any input.
> >
> > What I have been thinking is to use a sync separator (LM 1881 from National
> > Semi)
> > This chip outputs horizontal sync, vertical sync and odd/even field
>  information.
> > Giving the PIC these signals will enable it to determine the start of each
> > frame and
> > also each line.
> >
> > The problem is that a line lasts only 64 uS, and the video signal therefore
>  has
> > to be sampled 400 times to get a horizontal resolution of 400 pixels.
> > At least this is what I'm aiming for.
> > I don't need more than 8 bits resoulution on the sampling, probably less.
> >
> > Another problem is that I will need some kind of buffering, probably the
> > entire frame, since the PC-parallell port is pretty slow.
> > Maybe using ripple counters to address some kind of memory will do the
> > trick? The PIC would of course control everything.
> >
> > I'm planning to use (and don't you dare laugh :-))  the 16C84 in this
 project,
> > mostly
> > because I don't have a programmer that supports anything else.
> > (My programmers are both the PICBlaster and the AN589 type. I've been
> > using the PIP-02 software for the PICBlaster and different types of software
>  for
> > the AN589)
> >
> > Any suggestions, good ideas etc?
> >
> > Cheers
> >
> >  -Oyvind
> >
> > ==========================================================
> > 'Oyvind Kaurstad, R & D Engineer, ABB Flexible Automation'
> >
> > Email : oyvind.kaurstad@nofac.abb.no
> >
> > //////// My worlds are colliding! - George Costanza \\\\\\\
> > ===========================================================
>
> I think you need buffering the entire frame. If you use DRAM then page
> mode is fast enough. It is possible to use the build in memory refresh
> counter, but it is more slow than page mode. I suggest that you use two
> memory banks, write four times to the first bank (page mode) while you
> refresh ( with internal counter ) the other. The timing is more fast than
> PIC16C84 handles and you need some external logic or a PLD to do it.
> PIC16C84 is fast enough to handle the high column adresses.
>
> Regards,
> Jens Dyekjfr Madsen
        Hi,
It-s good idea but any of IBM likes PC do not handle this data stream
on Centronix Port...You must have a frame bufer (H X Res X ver_lines)X8
bites capacity.
        Best regards,
                Saras.