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ADV7842 interrupts stop if allowed to free run on different format to input

Question asked by adhawkins on Apr 11, 2013
Latest reply on Apr 26, 2013 by adhawkins

Hi,

 

I'm setting up the 7842 in Component YPbPr mode, and monitoring the CP lock, CP unlock and STDI valid interrupts to detect changes in the input format. When I receive these interrupts, I check the STDI Valid status bit, and then read the Component HFreq and Total height registers to determine the new input format. If this is a format valid for our device, I update the settings for VID_STD and output frequency to have the 7842 output this new format. If the format is not valid for our device, I make no changes, allowing the 7842 to free run and generate a default solid colour.

 

If I update the VID_STD settings and output frequency to output the newly detected format, I then continue to receive interrupts as expected. However, when I leave these settings at their previous values to enable the 7842 to free run and generate a default solid colour, I no longer receive interrupts when the input format changes again. If I poll the STDI Valid, Component HFreq and Total Height registers, then I do see changes as expected.

 

How can I continue to receive these interrupts when the part is free running? I'm trying to avoid polling if I can avoid it.

 

Thanks

 

Andy

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