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I wanted to know if anyone is familiar with the problem we are facing with the output video of the ADV7321:

In NTSC mode, we perform I2C cycles over the bus which the ADV7321 is controlled by, with several other video components.

It can take some time, but after N cycles over the I2C bus we have noticed that the monitor turns from color picture into B&W picture.

At this point, a  VM700 scope connected to the ADV7321 output turns to present a "No Burst" title on its screen. We examined the burst shape

and found it changed from standard NTSC format to be in the PAL burst frequency (~4.4Mhz) but other characteristics of the signal are still in NTSC format.

Furthermore, forcing a "color bar" output over the ADV7321 at this point, generates also a faulty ("no burst") B&W picture

Can it be that a faulty I2C cycle caused this at the ADV7321? If so, how to take it out of this phase (we managed to to it only with power down) ?

I will appreciate any help with this strange behavior.



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