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ADV7842 CEA 1280x720 30hz Detection

Question asked by MatthewDSE on Mar 24, 2014
Latest reply on Mar 25, 2014 by MatthewDSE



We are using an ADV7842 as a front end analog to digital decoder in a set top box design.  Our customer has a HDMI camera and has asked us to support its 1280x720 30hz resolution.   They have supplied the video signal timings, which are listed below.  I don't have their camera and am testing with a video pattern generator that has been programmed  with the exact values.  The problem I have is that the VERT_FILTER_LOCKED (HDMI reg 0x07[7]) will not lock.  The horizontal measurement parameters such as the front porch, active width, back porch, etc. match what I programmed the pattern generator with, but the vertical measurements are bogus due the vertical not locking. I have no problems detecting other SD or HD resolutions up to 1080p60 and am stumped why this one is a problem.


Can anyone please advise why this particular resolution will not lock?  The customer says the camera timing matches the CEA-EIA-851-E specification. 


Here is the 1280x720 30hz video timing information from our customer;


Pixel Clock Freq: 74.25MHz

Horizontal Freq: 22.50 KHz

Vertical Freq: 30Hz


Vsync: 5 pix

Vbackporch: 20pix

Vtotal: 750pix

Vactive: 720


Hsync: 40pix

Hpackporch: 1720 pix

Htotal: 3300 pix

Hactive: 1280


Best Regards,