I have one open query from the Premier Support Case. Please reply.
Case Number Case Subject
00290416 PCIe Pin selection
Case 00290416 is currently set to closed-pending. All questions related to the request has been answered and since no further question, case has been set to closed-pending.
The last question and answer session is copied and paste as following. Please advice if there is further questions:
Can you please check and let me know, will there be an issue, if the RREF pin is connected directly to GND and not through a 2K resistor?
Yes there will be an issue. Most analogue circuit require a reference voltage from RREF. without the 2k resistor, the expected reference voltage will not be correct.
Hence, this could cause PLL to not lock, Rx detections circuit to not work.
We noticed one difference (RREF pins) in the pin file generated with Quartus 16 & Quartus 18 version of the tool.
In Q16, the pins A29 & AP29 are shown as GND, because of which on our board we missed to connect this via a 2K resistor?
In Q18, the pins A29 & AP29 are shown as RREF pins.
RREF pins are to be connected externally. Quartus does NOT pull the voltage internally to GND or VCC. What you observed is just change in naming by Quartus. Quartus does not program the RREF pins.
Now we plan to bring this change(connect these pins to GND via 2K resistor). Do you think this will resolve the PCIe detection issue? By theory if the RREF resistor is not connected, this could cause PLL not to lock, Signal Detect circuit not to work, Receiver detect circuit not to work. Hence, resolving this definitely will have an impact of PCIe link. Hence, there is a good chance you could get your issue resolved by tying the RREF pin to 2K resistor. If still unable to resolve, please continue debugging the PCie link failure using the provided FTA.