i have pretty much exactly the same issues that you are seeing with the errant syncs when running through the 9880, although i dont see spotty video in this case. my scope captures do not show any reason why the errant syncs occur, except that when i get an errant vysnc and hsync, the errant hsync is always trailing the errant vsync by approx 4ns, or you can see it as each vsync and hsync are lined up with the control bit timing within the CH0 stream during inactive DE. So looking at the CH0 through active dif probes and the snyc outputs doesnt show anything that would allude to why the errant syncs occur, but i'm not too sure if there's a delay between the control bits on CH0 to when the output of the syncs occur.
i have this issue in through my AD FAE and hope to get answers soon. I've attach some scope shots that might be helpful:
datach0errantvsync.bmp is an errant vsync while looking at CH0 stream
errantvsynctop3.bmp, top trace is vsync and bottom trace is hsync and the errant hsync occurs approximately 14 ns after a valid low to high transition, notice the delay of ~4ns from the errant vsync to hsync.
Can you capture a full VSync pulse with both leading and trailing edges and the glitch. I'd like to see where the glitch occurs within the VSYNC pulse.
The errant sync pulses occur throughout the frame at random periods, however i'm attaching a scope shot that shows both the hsync and vsync glitches while DE should be active, not shown but the hsync and vsync are negative polarity and the glitches occur during the high side of both syncs.
A couple of things to try in order:
1) Invert the clock signal and see if this helps, check Register 0x24 bit 0. Of course the clock sink would have to handle the inverted clock correctly.
2) Increase the 1.8V supply to 1.85-1.9V (pins 30, 32 and 48 (if possible)
3) Lower the 3.3V supply to 3.0V (pins 10, 90, 100) (if possible)
Let me know how this works.
I'm figuring out a way to change the voltage on the 1.8 and 3.3V. Can you tell me the reasoning behgind that suggestion and would i have to chnage both or one at time?