Is it possible to get an eye diagram on a TDS784?


dnmeeks
 

InstaVu seems like the right place to start, but I don't know a way to trigger properly (on both edges). Has anyone done this on this vintage scope?
Thanks
Dan


Mark Goldberg
 

You really should have active data if you want a worst case eye diagram.
Intersymbol interference, jitter and line reflections will vary depending
on the data. Assuming your data has 2 or more states, transitions at fixed
intervals,is random and has some sort of preamble that is fixed, you can
trigger on one edge in the preamble and then look at the eye later down the
data where it is random and see the worst case with a long persistence
setting. I don't know if this will work for your data. Hold off may help
triggering where you want.

Regards,

Mark

On Fri, Aug 17, 2018 at 9:46 AM, dnmeeks <dan-meeks@...> wrote:

InstaVu seems like the right place to start, but I don't know a way to
trigger properly (on both edges). Has anyone done this on this vintage
scope?
Thanks
Dan




EricJ
 

Yes it's definitely possible on TDS7xx. It's a bit better on the later versions (i.e. 7xxD vs 7xxA) because InstaVu was improved to include grading. Intensity is visible through color mapping. You want to trigger on only one waveform, then change horizontal position to 3-5 events further down the line and use your persistence adjustment to fine tune your eye. 
--Eric
Sent from my Samsung Galaxy smartphone.

-------- Original message --------From: Mark Goldberg <marklgoldberg@...> Date: 8/17/18 12:28 PM (GMT-06:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Is it possible to get an eye diagram on a TDS784?
You really should have active data if you want a worst case eye diagram.
Intersymbol interference, jitter and line reflections will vary depending
on the data. Assuming your data has 2 or more states, transitions at fixed
intervals,is random and has some sort of preamble that is fixed, you can
trigger on one edge in the preamble and then look at the eye later down the
data where it is random and see the worst case with a long persistence
setting. I don't know if this will work for your data. Hold off may help
triggering where you want.

Regards,

Mark


On Fri, Aug 17, 2018 at 9:46 AM, dnmeeks <dan-meeks@...> wrote:

InstaVu seems like the right place to start, but I don't know a way to
trigger properly (on both edges). Has anyone done this on this vintage
scope?
Thanks
Dan




Jim Ford
 

Usually you want to trigger on the clock.  That way all the data transitions overlap and form the eye.  Eye closure top to bottom indicates noise, ringing, and other amplitude anomalies.  Eye closure side to side indicates jitter and other time-based anomalies.  But you probably knew that.


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Mark Goldberg <marklgoldberg@...> Date: 8/17/18 10:28 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Is it possible to get an eye diagram on a TDS784?
You really should have active data if you want a worst case eye diagram.
Intersymbol interference, jitter and line reflections will vary depending
on the data. Assuming your data has 2 or more states, transitions at fixed
intervals,is random and has some sort of preamble that is fixed, you can
trigger on one edge in the preamble and then look at the eye later down the
data where it is random and see the worst case with a long persistence
setting. I don't know if this will work for your data. Hold off may help
triggering where you want.

Regards,

Mark


On Fri, Aug 17, 2018 at 9:46 AM, dnmeeks <dan-meeks@...> wrote:

InstaVu seems like the right place to start, but I don't know a way to
trigger properly (on both edges). Has anyone done this on this vintage
scope?
Thanks
Dan




Mark Goldberg
 

Add one assumption to my statement:

Assuming your data is self clocking with no clock available, has 2 or more
states, transitions at fixed
intervals,is random and has some sort of preamble that is fixed, you can
trigger on one edge in the preamble...


I assumed a clock was not available, which was the case for most of the
work I did, so the data was self clocking and synced to a preamble.

Of course, if a clock is available, that is better to trigger on it and all
transitions can overlap, but I did not have that luxury and wanted to show
how it could be done even in the no clock case. If you have a sufficient
persistence, you can still see the worst case. If there is a reflection in
the line that is several bits away, it's effects won't be seen until later
in the data.

Regards,

Mark

On Fri, Aug 17, 2018 at 11:53 AM, Jim Ford <james.ford@...> wrote:

Usually you want to trigger on the clock. That way all the data
transitions overlap and form the eye. Eye closure top to bottom indicates
noise, ringing, and other amplitude anomalies. Eye closure side to side
indicates jitter and other time-based anomalies. But you probably knew
that.


Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Mark Goldberg <
marklgoldberg@...> Date: 8/17/18 10:28 AM (GMT-08:00) To:
TekScopes@groups.io Subject: Re: [TekScopes] Is it possible to get an eye
diagram on a TDS784?
You really should have active data if you want a worst case eye diagram.
Intersymbol interference, jitter and line reflections will vary depending
on the data. Assuming your data has 2 or more states, transitions at fixed
intervals,is random and has some sort of preamble that is fixed, you can
trigger on one edge in the preamble and then look at the eye later down the
data where it is random and see the worst case with a long persistence
setting. I don't know if this will work for your data. Hold off may help
triggering where you want.

Regards,

Mark


On Fri, Aug 17, 2018 at 9:46 AM, dnmeeks <dan-meeks@...> wrote:

InstaVu seems like the right place to start, but I don't know a way to
trigger properly (on both edges). Has anyone done this on this vintage
scope?
Thanks
Dan









Jim Ford
 

True, Mark.
It has been several decades since I have created or observed an eye diagram, after all.  I was thinking of how data patterns with long strings of ones or zeroes might not show the entire picture.  And I discount RZ, PAM, and other non-NRZ data formats, since I haven't worked with them.  Mainly frequency domain work these days, although for time-domain work I do prefer Tektronix products.
Thanks for adding to the discussion.   You have obviously had your "hands dirty" more recently than I have!


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Mark Goldberg <marklgoldberg@...> Date: 8/17/18 12:16 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Is it possible to get an eye diagram on a TDS784?
Add one assumption to my statement:

Assuming your data is self clocking with no clock available, has 2 or more
states, transitions at fixed
intervals,is random and has some sort of preamble that is fixed, you can
trigger on one edge in the preamble...


I assumed a clock was not available, which was the case for most of the
work I did, so the data was self clocking and synced to a preamble.

Of course, if a clock is available, that is better to trigger on it and all
transitions can overlap, but I did not have that luxury and wanted to show
how it could be done even in the no clock case. If you have a sufficient
persistence, you can still see the worst case. If there is a reflection in
the line that is several bits away, it's effects won't be seen until later
in the data.

Regards,

Mark


On Fri, Aug 17, 2018 at 11:53 AM, Jim Ford <james.ford@...> wrote:

Usually you want to trigger on the clock.  That way all the data
transitions overlap and form the eye.  Eye closure top to bottom indicates
noise, ringing, and other amplitude anomalies.  Eye closure side to side
indicates jitter and other time-based anomalies.  But you probably knew
that.


Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Mark Goldberg <
marklgoldberg@...> Date: 8/17/18  10:28 AM  (GMT-08:00) To:
TekScopes@groups.io Subject: Re: [TekScopes] Is it possible to get an eye
diagram on a TDS784?
You really should have active data if you want a worst case eye diagram.
Intersymbol interference, jitter and line reflections will vary depending
on the data. Assuming your data has 2 or more states, transitions at fixed
intervals,is random and has some sort of preamble that is fixed, you can
trigger on one edge in the preamble and then look at the eye later down the
data where it is random and see the worst case with a long persistence
setting. I don't know if this will work for your data. Hold off may help
triggering where you want.

Regards,

Mark


On Fri, Aug 17, 2018 at 9:46 AM, dnmeeks <dan-meeks@...> wrote:

InstaVu seems like the right place to start, but I don't know a way to
trigger properly (on both edges). Has anyone done this on this vintage
scope?
Thanks
Dan









Kevin Oconnor
 

Well an eye diagram is really just the envelope of all hi/lo & early/late levels & transitions in a data stream. Assuming that you can trigger off something relative to the stream, even old scopes with analog or digital persistence can do a decent job showing an eye.
My HP54503A monochrome 500Mhz has a trig/display mode that will do that.
Of course some of the more fancy Tek/HP scope with color planes can colorized the eye with more interesting data. Which I had one of those sometimes!

Kjo