PDA

View Full Version : modify example 512x384



Guyvo
09-14-2007, 01:58 AM
Hi props,

The example of the VGA 512x384 works on my TFT lcd but if I try it on my LCD TV (PC input) it shows nothing at all. (mode not supported on the screen) Now this can be normal because of the several frequencies that much match to trigger the signal. The demo says also that it signals as a 1024 x 768 67Hz. I looked in the tech spec of my screen and I have following modes for 1024·available:

H freq(khz)······ V freq (HZ)·· Pix clk (MHZ)··· H/Vpol
48.364·············· 60············· 65.000············· -/-
56.476·············· 70.069········75.000············· -/-
60.023·············· 75.029······· 78.750············· +/+

Can I found somewhere some formulas to calculate new values that fit the above frequencies ? eg. How can I determine the 67Hz out of the params of the example ? In what can I compare the H/V sync hn /vn params +/- 1/0 here ?

I run a prop with 5Mhz crystal.

The settings of the demo are showed below.

' 512x384 settings - signals as 1024 x 768 @ 67Hz
· hp = 512····· 'horizontal pixels
· vp = 384····· 'vertical pixels
· hf = 8······· 'horizontal front porch pixels
· hs = 48······ 'horizontal sync pixels
· hb = 88······ 'horizontal back porch pixels
· vf = 1······· 'vertical front porch lines
· vs = 3······· 'vertical sync lines
· vb = 28······ 'vertical back porch lines
· hn = 1······· 'horizontal normal sync state (0|1)
· vn = 1······· 'vertical normal sync state (0|1)
· pr = 35······ '35 pixel rate in MHz at 80MHz system clock (5MHz granularity)
Thx
Guy