Re: [IBIS] BIRD119: IBIS-AMI New Reserved Parameters

  Tstonefile

The following section needs some discussion.

    The default TX and RX node maps assume that the high-speed serial
    channel
    flows from left to right, and that analog model S parameters flow
    from left
    to right. Transmitter input ports are assumed to be the left hand (Near)
    ports 1 and 3, while the pad ports are assumed to be the right hand
    (Far)
    ports 2 and 4. Receiver pad ports are assumed to be the left hand (Near)
    ports 1 and 3, while the output ports are assumed to be the right
    hand (Far)
    ports 2 and 4.

    Transmitter Default Port Map
    Port Description
    1 Input true port
    2 Pad true port
    3 Input complement port
    4 Pad complement port

    Receiver Default Port Map
    1 Pad true port
    2 Output true port
    3 Pad complement port
    4 Output complement port

Comments

   1. In essence, the authors are saying that the network is
      unidirectional, with no transmission coefficients in the reverse
      direction. If this is the case, channel reflections will
      terminate at the package/die pad boundary and not propagate into
      the summer. (i.e. - real energy is lost in the simulation). As
      long as the extraction of the analog circuit touchstone model was
      performed at a sufficiently high impedance such that all
      reflections from the hypothetical Tx or Rx summer have been
      incorporated into the die-to-package path reflection coefficient
      then there is not a problem. Effectively a large reflection
      boundary is formed that meets the conditions outlined in the
      Tstonefile discussion above. If not, if the die side ports are
      terminated at a 50 ohm-ish characteristic impedance, then the
      resulting reflected waveform will be incorrect.
   2. Comment 1 necessarily requires clarification on Tx and Rx
      termination, how it will be incorporated, and interaction with
      touchstone file port impedance.
   3. Port assignments seem to be oriented towards signal flow
      direction, rather than universality at the die-package boundary.
      I would argue for port numbering relative to the die pad and
      hypothetical receiver/driver high impedance summer. In this way
      the default node numbering is relative to the die and die pads,
      just as package models should also be relative to the die pads and
      bumps. Otherwise, mistakes in modeling will be made.
   4. What about multiple channels for crosstalk modeling?
   5. I'd argue for a similar construct for packages. Without a way to
      encapsulate package models and concatenate them in the standard, a
      significant part of the channel is missing.
   6. Or ... if multiple channels are modeled with the Tstonefile
      construct, then the model can be easily extended by the developer
      to incorporate the complete cascade of the package and the die
      analog models. To be consistent with IBIS, the package parasitics
      in the IBIS package fields would be zeroed out.

Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax

http://www.teraspeed.com

Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC

On 10/6/2010 11:54 AM, Mirmak, Michael wrote:
>
> The enclosed BIRD 119, IBIS-AMI New Reserved Parameters, is
> distributed on behalf of Walter Katz, Mike Steinberger and Todd
> Westerhoff of SiSoft. It will be introduced at the next IBIS Open
> Forum meeting.
>
> A full list of BIRDs, their status and association with particular
> IBIS versions may be found at http://www.eda.org/ibis/birds/.
>
> Please note that the enclosed file is a "pointer" to a separate PDF
> file of the BIRD text, as the IBIS e-mail reflector does not permit
> redistribution of binary files. The enclosed file is identical to the
> ASCII file on the BIRD list at the URL above. The complete BIRD text
> is available at:
>
> http://www.eda.org/ibis/birds/bird119/bird119.pdf
>
> Michael Mirmak
>
> Intel Corp.
>
> Chair, IBIS Open Forum
>
>
> --
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