[Open-graphics] video head 0 module template

[Timothy Miller]

On 10/5/06, Simon Persson <simper-2 at student.ltu.se> wrote:
> On Monday 02 October 2006 23:32, Timothy Miller wrote:
>
> >
> > // Since this is a DDR interface, it is convenient to use a DDR FF
> > // to provide the clock signal.  IIRC, we want data0 to appear with
> > // the rising edge of the clock, so we want to produce it on the
> > // negative edge.
> > ddrff1 ff0 (.Q(dvi_m_clk), .C0(clock), .C1(~clock), .D0(1'b0),
> > .D1(1'b1), .OE(1'b1));
> > ddrff1 ff1 (.Q(dvi_s_clk), .C0(clock), .C1(~clock), .D0(1'b0),
> > .D1(1'b1), .OE(1'b1));
> >
>
> I'm not sure I understand the purpose of these... As I see it they only invert
> and add a slight delay.

What they do logically is just transfer different data on opposing
edges of the clock.  But a normal register cannot behave this way.
Xilinx has supplied special I/O registers that are DDR-capable, and we
have to manually instantiate them.

>
> I've been working on generating the syncs and blank signal, I have something
> working but now I've been using clock_2x for the counting and just realised
> that all the horisontal timing numbers I've seen are even. So I could change
> it to use clock instead and cut the frequency needed in half. A good thing I
> guess?

Please.  We want to use clock_2x for as little as possible.

> Also... should I add a single link dvi mode before I post my solution?

That would'nt be a bad idea.  We'll have to figure out if anything
special needs to be done to select between the modes.  How do you tell
the slave transmitter to do nothing?  Turn off its clock?  I don't
know.  But I'm pretty sure we just want to send data through the
master transmitter.

Feel free to cheat big time.  Rather than trying to send out the same
image via single-link as via dual, just throw away the odd pixels and
adjust the counters a bit.  What we see isn't as important as that we
can see it and use that to verify that the board is wired correctly.

> And... final question... gtkwave won't start on my ubuntu edgy, it complains
> about "signalfont courier 14 missing". I saw a bugreport on this but no
> solution. Has anyone here run into that problem? I'm using ivi to view the
> vcd file now, are there any better alternatives?

I guess I'm lucky that I couldn't even get Edgy to install.  :)

Can you install a Dapper version?  Or is it the same version of
GTKWave and some other system problem?

I try to avoid manually installing apps, because the package system
can't track them.  But since you're using an unstable release anyhow,
have you considered downloading the source to GTKWave, building it,
and installing it manually?