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PCIe Fingers not Connected in Hyperlynx

Question asked by radupont on Apr 1, 2020
Latest reply on Apr 2, 2020 by radupont

I am performing a multi-board simulation of a PCIe 3.0 interface of a PCIe carrier and a module in Hyperlynx VX 2.5.  Upon exporting the to a s-parameter model of the pairs that connect to the fingers on side A of the PCB it became evident that something was not connected in Hyperlynx.  If I select a C2H pair that connects to the side A fingers I see the following where the finger is not highlighted with the net.

The S-parameter model has a S31 of -200dB across frequency and the export to linesim does not have the buffer representing the connector connected to the remainder of the nets.  I did move the buffer up near the TLs to take a screenshot.  The buffer for A16/A17 (PCIe Fingers) are disconnected from the other portions of the nets.

The same net in PADs Layout viewer shows full connectivity between the transmission line traces and the PCIe fingers.  The HL file was exported months ago by a contractor for our customer and I am not able to export it again.

If I perform the same steps on a differential pair connected to fingers on side B of the PCB everything is fine.  The fingers highlight with the traces and the S-parameter has expected S31 and the net exports to linesim with everything connected.

I am not sure what is going on.  Does anybody have any suggestions to resolve this issue?  I have a work around where I connect the fingers to the last transmission line and export the linesim to a S-parameter file that can be used for channel analysis using IBIS AMI models.  But I would be more confident if the entire pair exported directly from boardsim to a s-parameter file.  I would greatly appreciate any suggestions or advice.

Thank you!