FieldTR pins 2,6: overshoots
Without having any error in the communication, we have noticed that
there are overshoots on the differential signal from the FielDrive to
the FieldTR, i.e. FieldTR pins 2, 6.
We confirmed the same behavior on the Alstom master
board.
The signals on the other side of the FieldTR, the WorldFIp bus side
(i.e. FieldTR pins 5, 3), are
clean.
We also contacted Exoligent and they confirmed that they see those
overshoots in their designs (see mail below).
Note that the overshoots appear only on frames emitted by the FieldDrive
(tx frames).
Note also that the part of the masterFIP design that connects the
FielDrive to the FieldTR comes from the original Alstom boards.
From: Guillaume Trannoy [mailto:guillaume.trannoy@exoligent.com]
Sent: 11 April 2016 17:52
To: Evangelia Gousiou <Evangelia.Gousiou@cern.ch>
Cc: Exoligent - Bruno Lepvraud (bruno.lepvraud@exoligent.com)
<bruno.lepvraud@exoligent.com>
Subject: Re: overshoots on FieldTR pins 2,6
Hello Eva,
I have done measurements on one of our FIP device and we experienced the same behavior. (Sorry for the not really good quality of pictures).
PIN 2, 6 (6: Yellow, 2:Pink, Math:
Violet)
PIN 3, 5 (5: Yellow, 3:Pink, Math:
Violet)
Intuitively, I think it is normal because of inductive effect of FieldTR.
In my case and I think it is the same for you, the FieldDrive emits the frames. High switching time on the inductance formed by FieldTR causes the overshoots. And on the network side, signal is filtered by FieldTR and line.
In case of FieldTR transferring FIP frame to the FielDrive, signal doesn't show overshoots.
PIN 2-6 in case or receiving FIP
frame:
The design of FielDrive/FieldTR part I used, is the same as yours in masterFIP.
I believe that the overshoot could be predict with switching time of the
FielDrive and equivalent electrical circuit. But I think it is a normal
behavior.
I hope it could help you.
Best regards,
Guillaume Trannoy