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ADV7842 VGA Operation

Question asked by MatthewDSE on Aug 23, 2013
Latest reply on Sep 3, 2013 by mattp

Hello,


I need to support many of the standard VESA VGA resolutions with the ADV7842.  Can the ADV7842 be configured to pass VGA video through without free run and without having to first set the VID_STD[5:0] register to the specific input resolution?  When the primary mode was HDMI this was possible by setting the PRIM_MODE to 6 "HDMI-GR" and the VID_STD to 2.  However, in graphics mode if the VID_STD value is 000001'b only SVGA 60hz horizontal and vertical sync frequencies are generated.  If the input resolution changes to SVGA 72hz, the ADV7842 continues to generate SVGA 60hz horizontal and vertical sync frequencies.

 

My current work-around is to wait for an interrupt when the video mode changes, read the measurement info (LCF, LCVS, and FCL, etc.) to determine the input resolution and then finally set the VID_STD[5:0] with the detected resolution.  In our design it would be simpler if the ADV7842 could be configured once to generate the horizontal and vertical sync signals of the input resolution or no syn signals if there is no VGA input.

 

Sincerely,

Matthew

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