PAM-5 / 1000BaseT or on CSA8200? How to Trigger? - Page 1
Forum section: electronics / testgear

author: TheWaterbug
author_rank: Contributor
timestamp: January 24, 2024, 12:35:57 am
content: ¡Hola!I am trying to look at raw Gigabit / 10 Gigabit Ethernet waveforms on my CSA8200/80E04 (also have a DSA8300), but I have no idea how to trigger it:I have a pair ofRJ45-to-SMA adapter boxesthat allow me to carry a set of Ethernet signals over eight 50 Ohm coax cables, and then I’ve interrupted some of those 50 Ohm coax cables with a set ofdifferential pickoff boxesthat allow me to probe any pair with 10x attenuation on the scope:The chain of adapters and pickoffs seems to be ok, because I can successfully carry 10GBaseT traffic over the link. I’ve tested from NIC to NIC through this adapter chain, and I can successfully negotiate a10GBaseT link (800 MBaud/pair), and iperf reports throughput of ~9.40 Gbit/sec, which is the same as I get if I remove my gaggle of adapters and just connect the NICs directly with a Cat7/Cat8 cable. So 1000BaseT should be just fine, since it's only125 MBaud/pair.I have two different Tx signals from the pickoffs going into my scope (with 80E04 sampling head), and that's what I'm trying to get a PAM-5 trace out of.I was able to get anMLT-3 traceby using aneval board for the Microchip KSZ9031RNX Ethernet transceiver chip, where this board has a test point where I can extract the 125 MHz TX Clock signal. I connected the Ethernet jack of the Microchip board to a PC, via my cabling-and-adapter setup. Then I used the PC to force100BaseT, and brought up a link. The purple trace is the 125 MHz clock, and the green is Pin 1 from the 100Base-TX signal, as seen from the Microchip side. The yellow trace is the RX side, e.g. TX from the PC:If the 100BaseT link negotiates to the Microchip side:and if it negotiates to the PC side:I can draw some conclusions about performance at 1000BaseT because it just uses 5 levels instead of 3, at the same baud rate, but dangit, I want to see it!!!But I can't figure out how to trigger it. If I let the eval board negotiate at 1000BaseT, I just get cloud of dots.If I go into the Trigger menu and choose Pattern Sync, it says “Pattern Sync Module not available,” but when I go to the Mask menu, I can apply a Mask for Gigabit Ethernet.Do I need to buy some sort of license module in order to trigger on Ethernet? Or am I just doing it wrong?I want to see PAM-5!!! And eventually I want to do this with 10GBaseT signals.

author: points2
author_rank: Regular Contributor
timestamp: January 24, 2024, 10:51:30 pm
content: Hi !I don't understand your question :you want to see the PAM-5 signal (1Gb)- to take a picture of it ?- or to measure jitter/etc ?Regarding the 10G signal, honestly, 10GbE base-T (=copper) = sh...t (no one use 10GbE thru copper ; a non-sense given the power / signal integrity /etc)10Gb is thru fiber (single-mode is far better than MM) : that's all. My 2 cents...

author: TheWaterbug
author_rank: Contributor
timestamp: January 24, 2024, 11:32:00 pm
content: Quote from: points2 on January 24, 2024, 10:51:30 pmYes, I want to take a picture of the PAM-5, if that's possible. I'm not sure if it is.If I google image search for "1000BaseT PAM-5" I get a bunch of diagrams, and a very few eye diagrams.Most of the eye diagrams look like simulations, and the one legit scope capture is mine, from when I posted this same question to an Intel forum 2.5 years ago and got zero responses.