How to trigger PAM-4 signal from Stratix 10 TX SI kit?

Hello Nathan,

Thank you for your reply. We are able to create 25GBaud PAM-4 signals with a high-speed DAC and display eyes on our DCA without problems. (I have access to two DCAs that can do this and have tried both.) Our DCAs are not bleeding edge technology but still seem sufficient. The main constraints are (1) that the trigger cannot be too fast (I believe 2 GHz is the limit, I don't remember) and (2) the symbol rate should be an _exact_ multiple of the trigger signal rate. Because of this constraint, we've tried applying an external clock with a rate which divides the symbol rate to the various PLL clock inputs on the SI board, including the one for the specific e-tile that generates the SMA outputs (9A as I recall). We still can't get the signal to trigger. It's not just a matter of having a closed eye. We've tried external clocks in the 100-156.25 MHz range. I wonder if maybe our 500 mV input clock signal is too low? We are driving it single-sided, not differential. By the way, as you suggest, I can capture traces with a real-time scope, but this is not what we want. Thank you again for the help.