[ibis-macro] Fundemental Problems with Externam Models and IBIS-ISS
- From: "Walter Katz" <wkatz@xxxxxxxxxx>
- To: "IBIS-Interconnect" <ibis-interconn@xxxxxxxxxxxxx>
- Date: Wed, 12 Dec 2012 13:26:05 -0500 (EST)
All,
The two possible applications of [External Model] are SerDes/AMI, and
normal Buffer Models.
Normal Buffer Models are not LTI and therefore IBIS-ISS does not apply.
When IBIS-BSS (Buffer Subcircuits) is defined then one can consider adding
IBIS-BSS to [External Model]. IBIS-BSS is not LTI, uses PWL voltage
controlled sources, level sensors, and a time function. I point out that
IBIS would not consider EMD until IBIS-ISS was defined and approved.
SerDes AMI models do not have digital input and digital output. The A/D
and D/A converters make no sense. All of the stuff inside of [External
Model] makes no sense for LTI SerDes Tx and Rx models which just have
analog differential inputs and analog differential outputs. They are
always four port subckts. They can always be represented as an s4p, or the
IBIS-ISS subsckts described in BIRD 122.
The only functionality needed is to define some simple [Model] (or AMI
keywords) that either point to an s4p Touchstone file, or a couple of
simple template 4 port IBIS-ISS subckts.
So why have a complicated gobbledygook change to [External Model] when
[External Model] by definition does not address the needs of LTI,
SerDes/AMI buffers.
Walter
Walter Katz
<mailto:wkatz@xxxxxxxxxx> wkatz@xxxxxxxxxx
Phone 303.449-2308
Mobile 303.335-6156
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