Sarunas Cepulis wrote:
>
> Jens Dyekjaer 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 Dyekjaer 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.

I think about using external DRAM's as 514256 (used on most standard DRAM
modules). They has a CAS before RAS refresh counter test cycle which
read/write data sequential into the memory. To make it fast enough,
improve this cycle with reading more columns as in page mode. This
methode does not need Row / collumn multiplexers since it use the build
in counter for row addressing. Page mode manage 40ns cycle time on 70 ns
DRAM's, or about 25 MHz. It is possible to sample color bursts and do
color sampling too.

When entire frame is stored at high speed - then transmit it at low speed
during the parallel port.

Regards,
Jens Dyekjaer Madsen