Hi David,
I wasn't involved in the BIRD adding Ts4file to IBIS, but I have recently used
Ts4file in a SerDes IBIS-AMI model.
For my Rx model, I included the on-die termination in the Touchstone data, so
the default Rx_R being an open made sense to me. I did actually find a couple
of EDA tools in my testing that were messing up default values for these
parameters or reading them incorrectly. Fixes are in progress. 😊
The EDA tools should be ignoring all the analog characteristics from [Model]
like C_comp and [Power_Clamp]/[GND_Clamp], since Ts4file is meant to be a
complete replacement of the analog model.
The descriptions of this are found in the Transmitter Analog Circuit and
Receiver Analog Circuit sections on pages 306-307 of IBIS 7.1:
"For a Tx buffer, the transmitter circuit defines the analog buffer model
between the zero-impedance stimulus input voltage source and the buffer
terminals."
"For an Rx buffer, the receiver circuit defines the analog buffer model between
the buffer terminals and the high impedance input of the Rx Algorithmic model."
Regards,
Randy
-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx <ibis-macro-bounce@xxxxxxxxxxxxx> On
Behalf Of David Banas
Sent: Wednesday, January 26, 2022 11:49 AM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [EXT] [ibis-macro] Questions on recent updates, re: on-die
S-parameters.
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Hello IBIS-AMI on-die S-parameter usage experts,
I'm trying to catch up w/ the latest revisions to the standard in this regard
and have a couple questions:
1. Why was the choice made to use zero Ohms and open circuit for the default
values of: Tx_R and Rx_R, respectively, as opposed to the reference impedance
of the Touchstone data?
2. Is there any explicit language in the current (v7.1) version of the spec.,
which directs the tool vendor to ignore [Power_Clamp]/[GND_Clamp] keywords in
the *.IBS file when Tx_R/Rx_R parameters are encountered in the *.AMI file?
Thanks!
-db
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