Mauricio Giovagnini wrote:

> Can you point me to where you read about the timings? That's 
> the main info I would like to know about.  I read many about 
> the implementation (everything done) but not about how the 
> signal is handled.

Here:
http://forum.microchip.com/tm.aspx?m=199298
and at http://piccoder.co.uk

Into the source (interrupt.c file) I cut'n'pasted the timings.


Horizonal Timing

Horizonal Dots         640     640     640
Vertical Scan Lines    350     400     480
Horiz. Sync Polarity   POS     NEG     NEG
A (us)                 31.77   31.77   31.77     Scanline time
B (us)                 3.77    3.77    3.77      Sync pulse lenght
C (us)                 1.89    1.89    1.89      Back porch
D (us)                 25.17   25.17   25.17     Active video time
E (us)                 0.94    0.94    0.94      Front porch

          ______________________          ________
________|        VIDEO         |________| VIDEO (next line)
     |-C-|----------D-----------|-E-|
__   ______________________________   ___________
   |_|                              |_|
   |B|
   |---------------A----------------|

Vertical Timing

Horizonal Dots         640     640     640
Vertical Scan Lines    350     400     480
Vert. Sync Polarity    NEG     POS     NEG
Vertical Frequency     70Hz    70Hz    60Hz
O (ms)                 14.27   14.27   16.68     Total frame time
P (ms)                 0.06    0.06    0.06      Sync length
Q (ms)                 1.88    1.08    1.02      Back porch
R (ms)                 11.13   12.72   15.25     Active video time
S (ms)                 1.2     0.41    0.35      Front porch

          ______________________          ________
________|        VIDEO         |________|  VIDEO (next frame)
     |-Q-|----------R-----------|-S-|
__   ______________________________   ___________
   |_|                              |_|
   |P|
   |---------------O----------------|

		

"VGA industry standard" 640x480 pixel mode

General characteristics

Clock frequency 25.175 MHz
Line  frequency 31469 Hz
Field frequency 59.94 Hz

One line

   8 pixels front porch
  96 pixels horizontal sync
  40 pixels back porch
   8 pixels left border
640 pixels video
   8 pixels right border
---
800 pixels total per line

One field

   2 lines front porch
   2 lines vertical sync
  25 lines back porch
   8 lines top border
480 lines video
   8 lines bottom border
---
525 lines total per field

Other details

Sync polarity: H negative, V negative
Scan type: non interlaced.

-- 
Ciao, Dario
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