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I am trying to interface a 24 Bit TFT screen.

But I am having a hard time understanding the need for Back and Front poch delays and how to calculate these ?

Virendra Kumar
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    They're throwbacks to the days of CRTs. – Ignacio Vazquez-Abrams Sep 12 '15 at 11:19
  • If you could add some more details – Virendra Kumar Sep 12 '15 at 11:30
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    If you need to decode a video waveform with the minimum number of vacuum tubes, these delays allow waveforms to settle to "black level" before and after the sync pulse while the scanning dot covers the screen "backwards", preventing ghosting and brightness variations in the picture. Not relevant to TFT screens, but there for compatibility with older systems. –  Sep 12 '15 at 11:30
  • @BrianDrummond Thanks for the detailed answer , So these delays are not required nowdays in TFT screens as these are controlled by very fast controllers. – Virendra Kumar Sep 12 '15 at 11:33
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    You need to follow the timing diagram the manufacturer provides, regardless of the names of the waveform features, or your success will not be assured. – Spehro Pefhany Sep 12 '15 at 11:49
  • Distant memory - aren't some signals placed on some of the 'porches' for secondary uses? – Russell McMahon Sep 13 '15 at 00:40

1 Answers1

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They are for compatibility with analog cathode-ray tube displays, so they are not really needed.

To compute them, use the algorithm specified in the Coordinated Video Timings standard. This algorithm is implemented in VESA's downloadable spreadsheet, and X.org's cvt tool.

CL.
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