bill@thd.tv.tek.com (William K. McFadden) (04/30/91)
I need to generate a signal compatible with all 640 X 480 "VGA
compatible" monitors, from the vanilla fixed rate to the mighty
multisync. I have determined the timings from several conflicting
documents, but need to know if they're correct. I have a 60 Hz spec.
and a 59.94 Hz spec. Any comments on the correctness or preference of
either would be apprecialted. I'll summarize any responses I get.
BTW, I'm beginning to wonder if there is an official specification,
because the various monitors and video cards seem to have different
timings for the same mode. This shouldn't be a problem as most
monitors allow a lot of slop. However, if there is an official
standard, I'd like to follow it (unless there is a good reason not
to).
60 Hz version:
Specification Time/Frequency Clocks/Lines
Dot Clock 25.452 MHz
Horizontal Rate 31.500 kHz
Vertical Rate 60.000 Hz
Pixel Period 39.290 nS
Horizontal Period 31.746 uS 808 clocks
Horizontal Blanking 6.601 uS 168 clocks
Horizontal Sync Width 3.772 uS 96 clocks
Horizontal Back Porch 1.886 uS 48 clocks
Active Line Time 25.145 uS 640 clocks
Horizontal Front Porch 0.943 uS 24 clocks
Vertical Period 16.667 mS 525 lines
Vertical Blanking 1.429 mS 45 lines
Vertical Sync Width 63.492 uS 2 lines
Vertical Back Porch 1.016 mS 32 lines
Active Frame Time 15.238 mS 480 lines
Vertical Front Porch 0.349 mS 11 lines
59.94 Hz version:
Specification Time/Frequency Clocks/Lines
Dot Clock 25.175 MHz
Horizontal Rate 31.469 kHz
Vertical Rate 59.940 Hz
Pixel Period 39.722 nS
Horizontal Period 31.778 uS 800 clocks
Horizontal Blanking 6.356 uS 160 clocks
Horizontal Sync Width 3.813 uS 96 clocks
Horizontal Back Porch 1.907 uS 48 clocks
Active Line Time 25.422 uS 640 clocks
Horizontal Front Porch 0.636 uS 16 clocks
Vertical Period 16.683 mS 525 lines
Vertical Blanking 1.430 mS 45 lines
Vertical Sync Width 63.555 uS 2 lines
Vertical Back Porch 1.017 mS 32 lines
Active Frame Time 15.253 mS 480 lines
Vertical Front Porch 0.350 mS 11 lines
--
Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077
bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill
Phone: (503) 627-6920 "SCUD: Shoots Crooked, Usually Destroyed"