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Old 10-21-2014, 09:22 AM   #1
ramkumar218
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Unhappy Horizontal and Vertical Timings for Display


Hallo Friends am very new to this topic,I have a doubt. In setting the parameters for Horizontal and Vertical timing for instance
Desired RR or Frame rate = 75 Mhz
HR=1440
VR=544
Could u kindly let me know what will be appropriate value or how can HGT1 and HSP be calculated for getting SH1 and SH2 value and also VSP to find SV2..
 
Old 10-21-2014, 03:42 PM   #2
Doc CPU
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Hi there,

it might be helpful if you could supply a little more information - as to what you're actually doing, where you need these parameters, and the specifications of the display you're using. Also, I'm not sure about some of your abbreviations. I gather that RR is Refresh Rate (sometimes called vertical frequency), HR is horizontal resolution, and VR is vertical resolution. I have no idea, however, what HGT1, HSP, SH1 and SH2 is.

Quote:
Originally Posted by ramkumar218 View Post
Hallo Friends am very new to this topic,I have a doubt. In setting the parameters for Horizontal and Vertical timing for instance
Desired RR or Frame rate = 75 Mhz
HR=1440
VR=544
Could u kindly let me know what will be appropriate value or how can HGT1 and HSP be calculated for getting SH1 and SH2 value and also VSP to find SV2..
First of all, the frame rate definitely isn't 75MHz, it's probably 75Hz. You're off by a factor of a million.

Multiply the frame rate (aka vertical frequency) by the number of scan lines (the vertical resolution), and you get the horizontal frequency. Note that many displays need a certain percentage of "invisible" scan lines for internal, technical reasons. So, with your figures I would take 600 scan lines (544 of which are visible), which yields a horizontal frequency of 600 * 75Hz = 45kHz.

Then multiply the horizontal frequency by the number of horizontal pixels (plus a few invisible ones), and you get the required pixel clock, that is, the speed at which your GPU has to generate its stream of pixels. Again, with your figures, I'm taking 1600 pixels across (1440 of which are visible), and I get a pixel clock of 1600 * 45kHz = 72MHz.

As I said, I have no idea what the other parameters are ...

By the way, I assume that your display is a flatscreen, not a CRT. Then there's no need to set a high refresh rate, since flatscreens are flicker-free by design. A refresh rate of 60Hz instead of 75Hz will do nicely. That would make the horizontal frequency drop to 36kHz, and the pixel clock to slightly below 60MHz, which is fine for many displays.

[X] Doc CPU
 
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Old 10-22-2014, 04:27 AM   #3
ramkumar218
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Unhappy Guard Time calculation

HI,
I am Trying to display different Refresh rate 20,60,75 in order to compare and show to the customer
Xfree86 modeline to fbset

The Horizontal Resolution is 1440 and vertical resolution is 544 i would like to know how can i calculate the fpllowing parameters
DCF(driving clock frequency,dot clock)
SH1 and SH2 ((SH1) indicates at which dot the horizontal sync pulse will begin. The third field (SH2) indicates at which dot the horizontal sync pulse will end)in order to calculate this there is formula used , SH1 = HR + HGT1(Horizontalguard time ), SH2 = SH1 + HSP(Horizontal sync pulse)

And also similarly
SV1 = VR + VGT ((Verticalguard time)but VGT is usually zero) and SV2 = SV1 + VSP(Vertical sync pulse)


DCF HR SH1 SH2 HFL VR SV1 SV2 VFL
if i know all the below mentioned value then i can calculate the Parameters
Horizontal Timing
Left Margin, Right Margin Hsync_len
Vertical Timing
Upper Margin,Lower Margin,Vsync_len
Refer this for Additionaldetails
http://www.tldp.org/HOWTO/html_singl...TO/#framesizes


I am stuck only with Calculating GuardTime HGT1,HSP(Horizontal sync pulse),Verticalguard time VGT,VSP(Vertical sync pulse) if u kindly help me how to calculate all this based on my specification it will be very helpful for me to proceed.
 
Old 10-22-2014, 09:58 PM   #4
jefro
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A long time ago you had to have data on card, then make your settings and hope you didn't burn up your card. Not sure if that can happen still but I offer warning.
 
  


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