Hello Everyone,
I decided to read through BIRD158 in great detail because of the disagreement
Walter and I have on whether this BIRD should appear in the same IBIS version
with BIRD189 or not. As I am reading BIRD158.6 in “final mode” (markups
hidden),
I am finding quite a few mostly editorial issues that should be corrected:
Correct the spelling of: “makde”
Correct the spelling of: “pachage”
Remove the extra “s”: “Stimulus s calculating”
Correct the spelling of: “cimpulse”
“Reserved Parameters” should either have an underscore between the words or
be spelled lower case. If using it as the name of the subparameter with the
underscore, it should always have the “s” at the end. Otherwise use lower
case first letters…
Change: “This BIRD defines new AMI Reserved Parameters Ts4file, Tx_V, Tx_R,
Rx_R.”
to something like:
“This BIRD defines four new AMI Reserved_Parameters: Ts4file, Tx_V, Tx_R, Rx_R.”
Change: “The ports 1 and 3 are at the Tx side, and ports 2 and 4 are connected
to the channel. Furthermore, the ports 1 and 2 correspond to the positive
signal path and the ports 3 and 4 to the negative signal path.”
to something like:
“Ports 1 and 3 are at the stimulus source side, and ports 2 and 4 are connected
to the buffer terminals. Furthermore, ports 1 and 2 correspond to the
non-inverting signal path and the ports 3 and 4 to the inverting signal path.”
Change: “The ports 1 and 3 are connected to the channel, and the ports 2 and 4
serve as the differential input to the Rx algorithmic model.”
to something like:
“Ports 1 and 3 are connected to the buffer terminals, and ports 2 and 4 serve
as the differential input to the Rx algorithmic model.”
Regarding the above sentence I wonder, whether the input to the Rx algorithmic
model is really at ports 2 and 4. Is this box really in series with the signal,
as if it was a package model? Or is the input to the algorithmic model at ports
1 and 3? (The BIRD160 approach with [External Model] actually allows for both).
Keeping the new capabilities described in BIRD189 in mind, the following two
sentences should also mention the possibilities of on-die interconnects:
“This Impulse Response characterizes the differential response of the Tx analog
buffer model, the Tx on-die interconnect model (if exists), the Tx package
model, the interconnect between the Tx component and the Rx component (the
channel), the Rx package model, the Rx on-die interconnect model (if exists)
and the Rx analog buffer model. The Touchstone file defined in this BIRD is to
be used for either the Tx analog buffer excluding the Tx package and Tx on-die
interconnect model and/or the Rx analog buffer model excluding the Rx package
and Rx on-die interconnect model.”
This is the reason I think BIRD158 and 189 should be added to the same IBIS
version.
I agree that this could be added with a later BIRD, but why shouldn’t we do it
now
“proactively” when we are fairly certain that BIRD189 will become part of the
spec?
If we decided to add BIRD158 to IBIS now and BIRD189 in a later version, we
would
have to write a “companion” BIRD to 189 immediately to adjust the connectivity
around these buffer models so that they would be consistent with the on-die
interconnect
capability described in BIRD189. I think we could save ourselves a bunch of
time
and work if we did this now and added the two BIRDs to the same IBIS version…
The
same argument applies to the following discussion item:
“#### For discussion: The model maker may want to inform the user and the EDA
tool that the Ts4file includes the package. Then a separate parameter is
needed. Alternatively, the model maker may provide the s4p data of the package.”
The above discussion will also have to include the on-die interconnect, made
possible
by BIRD189. Possibly through another additional parameter…
How many Tx_R parameters do we have? I only see one, so it should be singular
in the following sentence:
“For Tx models that have the Reserved Parameter Ts4file, the Reserved Parameter
Tx_V is required and the Reserved Parameters Tx_R are optional.”
This sentence should be changed from:
“In other words, for a Tx buffer, the Transmitter Circuit defines the analog
buffer model between the zero impedance stimulus input voltage source and the
channel.”
to:
“In other words, for a Tx buffer, the Transmitter Circuit defines the analog
buffer model between the zero impedance stimulus input voltage source and the
buffer terminals.”
Similarly, the next sentence should be changed from:
“For an Rx buffer, the Receiver Circuit defines the analog buffer model between
the channel and a high impedance probe at the input to the Rx Algorithmic
model.”
to:
“For an Rx buffer, the Receiver Circuit defines the analog buffer model between
the buffer terminals and a high impedance probe at the input to the Rx
Algorithmic model.”
Note that in the paragraph that discusses the drawing of the whole system,
the word “channel” is used in a different way:
“This Impulse Response characterizes the differential response of the Tx analog
buffer model, the Tx package model, the interconnect between the Tx component
and the Rx component (the channel), the Rx package model and the Rx analog
buffer model.”
Here, “channel” does not even include the package (or potentially the on-die
interconnect). This will confuse the reader, not knowing what really the
“channel” consists of.
Please change (we can’t mention “this BIRD” in text that goes into the spec:
“the other component’s contribution to the Channel Step Response (or just the
cimpulse response) follows the .ibs file description, as has been the case
before this BIRD has been introduced.”
to:
“the other component’s contribution to the Channel Step Response (or just the
impulse response) is described by the [Model] keyword in the .ibs file, as has
been the case before the Ts4file, Tx_V, Tx_R, Rx_R parameters have been
introduced.”
In the Definition section of Ts4file, change:
“This parameter contains the name of 4-port Touchstone file to be used in the
Analog Model Circuit. The If the file contains 4-port S-parameter data”
to:
“This parameter contains the name of the 4-port Touchstone file to be used in
the Analog Model Circuit. If the file contains 4-port S-parameter data”
In the Definition of Tx_R, we should probably use plural for the
resistor at the end of the sentence, since there are two of them:
“This parameter is optional and defines the value of the Tx_R series resistors
in ohms.”
While most of these comments are editorial in nature, my main point is
that with a minimal change we could make this BIRD consistent with BIRD189,
and doing that could save us a lot of additional work and time later when
BIRD189 is added to IBIS. I would highly recommend that we make these
changes to this BIRD now and add these two BIRDs together to IBIS.
Thanks,
Arpad
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