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Cyclone V using TPG -> CVO, Mode match is not behaving correctly, but I am getting video out


My c code sets the parameters for mode 1 as the data sheet states, and video output functions, but when I read the Video Mode Match register, I get garbage instead of the expected 0x00002.


When I try to re-write the registers in Mode 1 for a different resolution, the output does not work. I think it has something to do with the Mode Match register not working.


Is it allowable to rewrite the TPG resolution, I believe this functionality is ok.. is there any issues in the CVO recognizing the TPG resolution and matching?

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3 Replies



As I understand it, you observe some issue with the mode match register of the CVO which seems to be reporting incorrect values. However, the video output is still functioning OK. Mind further elaborate on the value that you have read back from the register during issue occurrence?


Just would like to check with you if you have had a change to perform a Modelsim simulation to see if can replicate similar observation? This would be helpful to further narrow down functionality related issue.


Just would like to check with you also if you use the CVO in the default mode configured during IP instantiation, is the ​mode match register behave correctly ie reading value of 0?


Just would like to check with you also if you have had chance to try with other Mode to see if it is specific to the Mode 1?


Thank you very much.


Best regards,

Chee Pin


Hi Chee Pin,


The good news is, I realized that I had instantiated the CVO I module rather than the CVO II module.


The bad news is that although I have gotten the mode match register to feed back the correct value, I am still having issues when swapping from 1920x1080 to 1280x720 or from 1280x720 to 1920x1080 from the TPG -> CVO.


Is there some special command priority to allow this to work correctly? The FPS is going from 30 to 60 in the case of 1920 to 1280 and 60 to 30 in the case of 1280 to 1920. Is there a disconnect due to the FPS change? There is no change in the input pll clock.




Caleb Soileau




Sorry for the delay. Based on my understanding, as long as you have configured the CVO with all the video modes that you will be feeding, the CVO will be able to automatically detect and switch to the new video format. Probably you can refer to the following design example in wiki to see if it is helpful?




Thank you.