Honored Contributor
Honored ContributorHi Thomas,
--- Quote Start --- you are right, it is DC connected. I think we have discussed this Vcm issue already in the past. The new board revision has this solved in a clean way. The revision we are talking about here has 1k3 pull-downs on both lanes to pull the Vcm into the correct region (quite ugly, but it works...). --- Quote End --- Rather than using two pull-downs of the same value, it can be useful to use two slightly different values, so that the static voltage difference on the input results in a logic 0 or 1 when there is no input. You can use SignalTap II logic analyzer to see what the input does when not connected to your cable. --- Quote Start --- I think the settings I use now (min. equalizer, max. gain) work very well, I haven't seen any error anymore. --- Quote End --- Excellent. --- Quote Start --- The eyeQ feature looks interesting, unfortunately Arria (and Stratix) are too expensive for our typical projects. Maybe we will use Arria 10 somewhen in the future... --- Quote End --- Yeah, I understand that they are expensive, but if you consider them a piece of test equipment, then you only need one. Another alternative is a PHY device from Vitesse with their VScope feature (another eye pattern tool). If you are interested, take a look at the Arria V devices and see if you can find a low-cost kit with the transceivers exposed, or create a simple board with an Arria V device. The eyeQ feature on the Arria V GZ devices works nicely at over 10Gbps. Cheers, Dave
