Honored Contributor
Honored ContributorJust in case anyone is wondering what would/could happen if these resistors are missing on designs using the Arria II GX device (in my particular case it was an EP2AGX45):
The reference input clock will most likely not work (probably because of wrong OCT calibration due to the missing reference resistor). I've just experienced this issue since we forgot to connect these pins according to the pin connection guidelines in our design. After somehow squeezing in a 2 kOhm resistor between ground and the FPGA ball via tiny wires (luckily this was an outside ball, so somewhat accessible) everything just started to work. I just wanted to share this information in case someone else runs across this same issue. Unfortunately there's not enough emphasis on the importance of this particular guideline (at least it doesn't provide information on the significance). Regards, Steffen
ContributorHi Steffen,
Your answer helps. Recently I am really struggling with this Calibration thing. From your words, "recalibration is required to fine tune the internal parameters of the TX PLL, RX PMA and TX PMA to ensure that they are optimal at your new data rates. This is also to ensure that XCVR blocks will operate as expected at the new data rates", can I say that if FPGA is not successfully calibrated / re-calibrated, XCVRs can still run, but may with lower performance than it should be?
If you are convenient, would you like to take a look a t this thread , some further description on my questions about A10 GX device calibration.
https://forums.intel.com/s/question/0D50P00004Gf0dgSAB/what-would-happen-if-transceiver-calibration-fails
Thanks, and happy weekend.
