[ibis-macro] Re: BIRD 158.2
- From: "Walter Katz" <wkatz@xxxxxxxxxx>
- To: "'Bob Ross'" <bob@xxxxxxxxxxxxx>
- Date: Fri, 17 May 2013 22:35:46 -0400 (EDT)
Bob,
Comments in-line, I sent (and attached this time BIRD 158.2) to the
reflector
Walter
From: Bob Ross [mailto:bob@xxxxxxxxxxxxx]
Sent: Friday, May 17, 2013 8:56 PM
To: wkatz@xxxxxxxxxx
Cc: 'IBIS-ATM'
Subject: RE: [ibis-macro] BIRD 158.2
Walter:
I did not see the draft BIRD158.2 attachment, but attached
are some editorial corrections to the content of BIRD158.1.
We can go over them at the ATM meeting.
The port 1 waveform is documented as
__
__| V = Tx_V,0, but should be V = 0, Tx_V
Similarly for
___
|__ should be V = Tx_V, 0
The words in the text are independent of the diagram.
(I cannot edit the diagram.)
My questions/comments are
1. I am not happy that we have to introduce a common mode
offset in contradiction to page 164, Step 4 of the Specification
which states that the input voltages are from -0.5 to 0.5.
WMK> You are comparing apples and oranges. The differential waveform is
Tx_V-0 = Tx_V when high and 0-Tx_V when low. So the differential waveform
is centered around 0.
I think it would be better to introduce Tx_Vp and Tx_Vn
where Tx_Vp defaults to 0.5V and Tx_Vn defaults to -0.5,
and the differential input is from V= Tx_Vn, Tx_Vp on port 1
and V = Tx_Vp, Tx_Vn on port 2. Then the parameters can
be passed in directly into the Converter Parameters of
BIRD160 to specify a differential stimulus that spans
-0.5 to 0.5. The common mode offset is disturbing and
assumes no common-mode to differential conversions.
Alternatively, we could enter in Tx_Vp and Tx_Vn to
match the actual voltage swing limits in the physical
Tx buffer.
Also the Definition of V_Tx is strange: "defines the
rail voltage of the I/O power supply in volts". Are we
really defining a power supply voltage or a voltage
swing limit?
Corners are already in sync, but I would rather put the
burden of syncing up Tx_Vp and Tx_Vn values on the EDA tool
than to create a technically unnecessary offset due to
weaknesses in other parts of the specification.
WMK> This is more realistic. In a normal differential driver both the
positive and negative side swing typically between 0V and PuRef. Thus one
can think of Tx_V as PuRef. When the input to the Tx is an equalized
waveform (e.g. output of Tx GetWave), then in affect the algorithmic model
is modulating PuRef. I think we have heard these exact words from David.
2. Should the Tstonefile name be changed to Tstonefile_s4p
since this if a pre-defined file for S-parameter 4-ports only?
Other predefined Tstonefile configurations are possible now
and in the future (for S, Y, Z parameters or for a
different number of ports). To "Tstonefile" seems
too generic when it applies to a specific configuration.
WMK> I used Tstonefile because this is the name that IBIS-ISS uses, I see
no need to change this.
3. Will the BIRD158 Reserved Parameters work without
BIRD160?
WMK> Yes
Bob
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Friday, May 17, 2013 3:45 PM
To: Michael Mirmak
Cc: IBIS-ATM
Subject: [ibis-macro] BIRD 158.2
MM,
I am formally submitting BIRD 158.2 to the Open Forum and requesting that
a vote be taken at the next Open Form to approve this BIR for inclusion in
the next release of IBIS.
I have made the change to specifically state that the Touchstone specified
by the reserved AMI parameter Tstonefile does not include the IBIS package
model, and described one method of generating an Impulse Response of the
channel suitable for use as input to the Tx AMI_Init function. I have not
made the change to the graphic that Bob requested because I do not know
how, because I think it is unimportant since the words in the text
describe exactly what to do, and because it can be done as part of the
editorial review. I will re-submit this BIRD if required due to any
editorial changes made during the Tuesday IBIS-ATM meeting.
Walter
Walter Katz
wkatz@xxxxxxxxxx
Phone 303.449-2308
Mobile 303.335-6156
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