vga

[ramsin]

Hello group,

I'm trying to understand how a VGA system works and as I was reading
an article at http://www.pldesignline.com/howto/205601374;jsessionid=5CZUVJGEKU1ZQQSNDLQCKH0CJUNN2JVN?pgno=2
I ran into a statement as following:

"he horizontal sync pulse, on the other hand takes place between
26,110ns and 29,880 ns of the overall interval."

I understood every part of the article but the thing I cannot digest
is 26110ns and 29880ns. How these numbers are calculate?

Any advice is appreciated.

Regards,
Amit

 

[Jonathan Bromley]

Hello group,

I'm trying to understand how a VGA system works and as I was reading
an article at http://www.pldesignline.com/howto/205601374;jsessionid=5CZUVJGEKU1ZQQSNDLQCKH0CJUNN2JVN?pgno=2
I ran into a statement as following:

"he horizontal sync pulse, on the other hand takes place between
26,110ns and 29,880 ns of the overall interval."

I understood every part of the article but the thing I cannot digest
is 26110ns and 29880ns. How these numbers are calculate?

They're not *calculated*, they're defined - the sync pulse for
VGA is supposed to be 3.77 microseconds wide, or thereabouts.

Can someone explain to me why the article proposes having *two*
pulses on HSYNC on every line?
--
Jonathan Bromley, Consultant

DOULOS - Developing Design Know-how
VHDL * Verilog * SystemC * e * Perl * Tcl/Tk * Project Services

Doulos Ltd., 22 Market Place, Ringwood, BH24 1AW, UK
(e-mail address removed)
http://www.MYCOMPANY.com

The contents of this message may contain personal views which
are not the views of Doulos Ltd., unless specifically stated.

 

[Mike Treseler]

Can someone explain to me why the article proposes having *two*
pulses on HSYNC on every line?

I think he is describing two fence posts
and one fence section. Hope he put waveforms
in his book.

-- Mike Treseler

 

[Amit]

I think he is describing two fence posts
and one fence section. Hope he put waveforms
in his book.

-- Mike Treseler

I got his book but it is full of typo mistakes in source code as well.
yet no waveform even one!

 

[Amit]

I got his book but it is full of typo mistakes in source code as well.
yet no waveform even one!

Anyway one thing I need to make sure is about timing. Some people use
clock cycles as criteria and some use number of pixels in each row.
Now, as far as I understand this is the timing as following so please
correct me if I'm wrong:

t0 t1 t2 t3
_____ __________________________ ________
| | | |
|_____| |_____|

and have:

t0 = 0
t1 = 5.66 us
t2 = 30.83 us
t3 = 31.77 us

Now, t1 ~ t2 range is view area

should I conisder t0 ~ t1 blank area?
What about t2 ~ t3?

Do you suggest I go with clock cycles? or number of pixels?

Regards,
Amit

 

[Mike Treseler]

Thanks for the review.

should I conisder t0 ~ t1 blank area?
What about t2 ~ t3?
http://www.epanorama.net/documents/pc/vga_timing.html

Do you suggest I go with clock cycles? or number of pixels?

Whichever you prefer.
I like clock ticks.

-- Mike Treseler

 

[Amit]

Thanks for the review.


Whichever you prefer.
I like clock ticks.

-- Mike Treseler

Thanks for your response. The problem I'm having in Altera (in wave
form) is that the clock stays high at 39.99ns so the counter won't go
further. What is wrong with my setting?

Regards,
Amit