FPGA Central

Hi All,
I am validating the DDR memory controller from 3rd party IP. With related
to the ODT settings of the DDR device, how to qualify and quantify which of
the 3 options(75,150,50Ohm) gives the better results.
I saw few waveforms on the website which shows an eye pattern of the w/f.
But i didnot understand how this is created using a differential signal
probed using an differential probe.
Thanks in advance
Regards,
Sudarshan


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Hi Sudarshan,
Our usual practice is to simulate with these three configuration(usually various models comes with the IBIS model of the same chipset) and see which has the least shoot and proper rise time in run interactive window of the tool. If possible use the DDR2 wizard(Hyperlynx8.0)and see the overall result in the excel sheet which tells you how many cases passed and failed.
All the best,
M Usman
-----Original Message-----
From: si-list-bounce (AT) freelists (DOT) org [mailto:si-list-bounce (AT) freelists (DOT) org] On Behalf Of sudarshan kr
Sent: Thursday, December 10, 2009 5:00 PM
To: si-list (AT) freelists (DOT) org
Subject: [SI-LIST] ODT Impedance on DDR2

Hi All,
I am validating the DDR memory controller from 3rd party IP. With related to the ODT settings of the DDR device, how to qualify and quantify which of the 3 options(75,150,50Ohm) gives the better results.
I saw few waveforms on the website which shows an eye pattern of the w/f.
But i didnot understand how this is created using a differential signal probed using an differential probe.
Thanks in advance
Regards,
Sudarshan


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"DISCLAIMER: This message is proprietary to Aricent and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error, please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. Aricent accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus."
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Hi,

usually just looking at a single trace or simulating just a view bits
gives only a qualitative answer, but no quantitative answer.
To decide on pass or fail you need to Calculate a timing budget.

This can be done by doing a (long enough) PRBS simulation with at least
3 (better 5) Signals (1 Victim and 4 Aggressors) and evaluate the
resulting dataeye according the spec. in DDR Case you would evaluate the
eye with AC/DC based setupHold times and adding the slew rate dependent
derating.
Additionally you add the Transmitter jitter and finally you will get a
pass or fail and how much margin the design has.

I have not seen the Hyperlinx wizard so far. Maybe somebody can comment
if this one does the eye evaluation ACDC based and add the Derating for
the DDR Memory ?

regards

Hermann

EKH - EyeKnowHow
Hermann Ruckerbauer
www.EyeKnowHow.de
Hermann.Ruckerbauer (AT) EyeKnowHow (DOT) de
Veilchenstrasse 1
94554 Moos
Tel.: +49 (0)9938 / 902 083
Mobile: +49 (0)176 / 787 787 77
Fax: +49 (0)3212 / 121 9008



Mashook Ahamed Usman schrieb:
> Hi Sudarshan,
> Our usual practice is to simulate with these three configuration(usually various models comes with the IBIS model of the same chipset) and see which has the least shoot and proper rise time in run interactive window of the tool. If possible use the DDR2 wizard(Hyperlynx8.0)and see the overall result in the excel sheet which tells you how many cases passed and failed.
> All the best,
> M Usman
> -----Original Message-----
> From: si-list-bounce (AT) freelists (DOT) org [mailto:si-list-bounce (AT) freelists (DOT) org] On Behalf Of sudarshan kr
> Sent: Thursday, December 10, 2009 5:00 PM
> To: si-list (AT) freelists (DOT) org
> Subject: [SI-LIST] ODT Impedance on DDR2
>
> Hi All,
> I am validating the DDR memory controller from 3rd party IP. With related to the ODT settings of the DDR device, how to qualify and quantify which of the 3 options(75,150,50Ohm) gives the better results.
> I saw few waveforms on the website which shows an eye pattern of the w/f.
> But i didnot understand how this is created using a differential signal probed using an differential probe.
> Thanks in advance
> Regards,
> Sudarshan
>
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request (AT) freelists (DOT) org with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request (AT) freelists (DOT) org with 'help' in the Subject field
>
>
> List technical documents are available at:
> http://www.si-list.net
>
> List archives are viewable at:
> http://www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
> "DISCLAIMER: This message is proprietary to Aricent and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error, please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. Aricent accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus."
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> For help:
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>
>
> List technical documents are available at:
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>
> List archives are viewable at:
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> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
>
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Disclaimer: I WORK FOR MENTOR GRAPHICS however, below is the header
from the DDR report. It is quite long, so it wraps in this email, but
you can see that we do compensate for derating.

The eye diagram does not use AC DC rules, it just shows the waveforms.
However, the timing measurements that are used in the spread sheet do
follow the DDR spec and use AC and DC thresholds when appropriate. The
wizard allows you to experiment with different ODT configurations.

Here is the header row for data bit simulation:

Net Name Pass/Fail Operation Driver Comp Ref Des &
Pin Name Receiver Comp Ref Des & Pin Name Associated
Clk/Strobe Net Name Associated Clk/Strobe Driver Comp Ref Des & Pin
Name Associated Clk/Strobe Receiver Comp Ref Des & Pin Name
Clk/Strobe Crossing Threshold Time, [ns] Setup Time (From Sim),
tDS, [ps] Min Setup Time, tDS(min), [ps] Base Setup Time,
tDS(base), [ps] Setup Derate Time Delta, d(tDS), [ps] Required Setup
Time, tDS(req), [ps] Setup Time Margin, tDS(margin), [ps] Hold
Time (From Sim), tDH, [ps] Min Hold Time, tDH - Initial Delay
Delta, [ps] Base Hold Time, tDH(base), [ps] Hold Derate Time Delta,
d(tDH), [ps] Required Hold Time, tDH(req), [ps] Hold Time
Margin, tDH(margin), [ps] Stimulus Offset, [ns] Comments

Regards,


Tony Cusanelli
Applications Engineer Consultant
http://www.mentor.com/products/pcb-s...-verification/
http://www.mentor.com/products/pcb-s...ducts/icx-tau/
Cell - 772-349-4363
Voice mail only 407-999-2334

-----Original Message-----
From: si-list-bounce (AT) freelists (DOT) org [mailto:si-list-bounce (AT) freelists (DOT) org]
On Behalf Of Hermann Ruckerbauer
Sent: Thursday, December 10, 2009 7:35 AM
To: sudarshan kr
Cc: Mashook Ahamed Usman; si-list (AT) freelists (DOT) org
Subject: [SI-LIST] Re: ODT Impedance on DDR2

Hi,

usually just looking at a single trace or simulating just a view bits
gives only a qualitative answer, but no quantitative answer.
To decide on pass or fail you need to Calculate a timing budget.

This can be done by doing a (long enough) PRBS simulation with at least
3 (better 5) Signals (1 Victim and 4 Aggressors) and evaluate the
resulting dataeye according the spec. in DDR Case you would evaluate the
eye with AC/DC based setupHold times and adding the slew rate dependent
derating.
Additionally you add the Transmitter jitter and finally you will get a
pass or fail and how much margin the design has.

I have not seen the Hyperlinx wizard so far. Maybe somebody can comment
if this one does the eye evaluation ACDC based and add the Derating for
the DDR Memory ?

regards

Hermann

EKH - EyeKnowHow
Hermann Ruckerbauer
www.EyeKnowHow.de
Hermann.Ruckerbauer (AT) EyeKnowHow (DOT) de
Veilchenstrasse 1
94554 Moos
Tel.: +49 (0)9938 / 902 083
Mobile: +49 (0)176 / 787 787 77
Fax: +49 (0)3212 / 121 9008



Mashook Ahamed Usman schrieb:
> Hi Sudarshan,
> Our usual practice is to simulate with these three
configuration(usually various models comes with the IBIS model of the
same chipset) and see which has the least shoot and proper rise time in
run interactive window of the tool. If possible use the DDR2
wizard(Hyperlynx8.0)and see the overall result in the excel sheet which
tells you how many cases passed and failed.
> All the best,
> M Usman
> -----Original Message-----
> From: si-list-bounce (AT) freelists (DOT) org
> [mailto:si-list-bounce (AT) freelists (DOT) org] On Behalf Of sudarshan kr
> Sent: Thursday, December 10, 2009 5:00 PM
> To: si-list (AT) freelists (DOT) org
> Subject: [SI-LIST] ODT Impedance on DDR2
>
> Hi All,
> I am validating the DDR memory controller from 3rd party IP. With
related to the ODT settings of the DDR device, how to qualify and
quantify which of the 3 options(75,150,50Ohm) gives the better results.
> I saw few waveforms on the website which shows an eye pattern of the
w/f.
> But i didnot understand how this is created using a differential
signal probed using an differential probe.
> Thanks in advance
> Regards,
> Sudarshan
>
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request (AT) freelists (DOT) org with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request (AT) freelists (DOT) org with 'help' in the Subject field
>
>
> List technical documents are available at:
> http://www.si-list.net
>
> List archives are viewable at:
> http://www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
> "DISCLAIMER: This message is proprietary to Aricent and is intended
solely for the use of the individual to whom it is addressed. It may
contain privileged or confidential information and should not be
circulated or used for any purpose other than for what it is intended.
If you have received this message in error, please notify the originator
immediately. If you are not the intended recipient, you are notified
that you are strictly prohibited from using, copying, altering, or
disclosing the contents of this message. Aricent accepts no
responsibility for loss or damage arising from the use of the
information transmitted by this email including damage from virus."
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request (AT) freelists (DOT) org with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request (AT) freelists (DOT) org with 'help' in the Subject field
>
>
> List technical documents are available at:
> http://www.si-list.net
>
> List archives are viewable at:
> http://www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
>
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List technical documents are available at:
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List archives are viewable at:
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Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu


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For help:
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List technical documents are available at:
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List archives are viewable at:
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Old (prior to June 6, 2001) list archives are viewable at:
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