Minutes from the 03 April ibis-atm meeting are attached.
IBIS Macromodel Task Group
Meeting date: 03 April 2018
Members (asterisk for those attending):
ANSYS: Dan Dvorscak
* Curtis Clark
Cadence Design Systems: Ambrish Varma
Brad Brim
Kumar Keshavan
Ken Willis
eASIC: David Banas
GlobalFoundries: Steve Parker
IBM Luis Armenta
Trevor Timpane
Intel: * Michael Mirmak
Keysight Technologies: Fangyi Rao
* Radek Biernacki
Ming Yan
Mentor, A Siemens Business: John Angulo
* Arpad Muranyi
Micron Technology: * Randy Wolff
* Justin Butterfield
SiSoft: * Walter Katz
Todd Westerhoff
* Mike LaBonte
SPISim: Wei-hsing Huang
Synopsys: Rita Horner
Kevin Li
Teraspeed Consulting Group: Scott McMorrow
Teraspeed Labs: * Bob Ross
The meeting was led by Arpad Muranyi. Curtis Clark took the minutes.
--------------------------------------------------------------------------------
Opens:
- None.
-------------
Review of ARs:
- None.
--------------------------
Call for patent disclosure:
- None.
-------------------------
Review of Meeting Minutes:
- Arpad: Does anyone have any comments or corrections? [none]
- Bob: Motion to approve the minutes.
- Mike L.: Second.
- Arpad: Anyone opposed? [none]
-------------
New Discussion:
BIRD189 and BIRD158 related issues:
- Discussion: Arpad noted that at one of last week's Interconnect meetings a
motion was made to define A_gnd as a global reference (node 0). That motion
had carried. Given that the definition of A_gnd had been resolved, Arpad
shared a new draft of his BIRD158 replacement. In the text defining the
triangle ground symbols, he proposed changing:
"...is the local reference node, A_gnd of the IBIS [Model]."
to:
"...is the global reference node, A_gnd."
Radek suggested that we not say "global", just "the reference node A_gnd."
Arpad changed the text to:
"...is the global reference node A_gnd, as defined in this
specification."
Bob noted his agreement. No one objected to the proposed text.
Arpad moved on to the issue of including "greater than 0" in the text defining
Tx_V and Rx_R (as had been proposed by Bob and the Quality group based on
their discussions about a contract for parser development). Arpad noted that
he thought it might be better to leave this unspecified. He noted that he
understood Bob's suggestion with respect to the parser development, but he
suggested handling common sense cases with a parser warning would be
sufficient and would leave more flexibility in the future. Radek noted that
negative values for Tx_V could be okay, so adding the "greater than 0" text
was probably going too far. Walter noted that in last week's meeting he had
given Rref_rising as an example of the many place in the IBIS specification
where we had not explicitly stated > 0. He said it was unnecessary to do it
with the BIRD158 parameters.
Bob said he thought it was best to have the "greater than 0" in the text. He
noted that for Walter's example of Rref_rising, a negative value would likely
have been caught by the parser based on other checks. Bob said there was no
reason to exclude the text simply because we hadn't been precise in previous
versions. He preferred to have the spec's language define what was in the
parser contract.
Arpad said that the IBIS spec isn't necessarily always the same as the parser
spec. Arpad moved to remove the "greater than 0" that had been added to the
BIRD draft, and to ask the Quality group to have the parser issue a warning
if Tx_V or Rx_R were non-positive. Curtis seconded. Bob asked for a vote
by organization. Results:
ANSYS - yes
Intel - yes
Keysight - abstain
Mentor - yes
Micron - yes
SiSoft - yes
Teraspeed Labs - no
The motion carried (5 Yes, 1 Abstain, 1 No). Arpad took an AR to incorporate
the changes discussed in the meeting and produce a new draft of his BIRD158
replacement.
Investigation into A_gnd history:
- Discussion: Arpad noted that he and Bob had an AR from the Interconnect
meeting to investigate A_gnd, which was originally introduced with [External
Model]. Arpad noted that the [External Model] section uses the term "port"
for what we generally call a terminal or node. Radek said this use of the
word "port" in the [External Model] section was incorrect.
Michael M. asked if we were trying to be entirely consistent with the multi-
lingual section of the specification. He noted that the word "port" was
used in that context because the Verilog or VHDL specifications had used the
term "port" in the way the we or SPICE normally use the term node. Arpad then
shared a private email he had drafted on this topic. He noted that "port" is
a keyword in VHDL-AMS that contains a collection of things that go in and out
of a model. So, port is a much broader concept in VHDL-AMS, more synonymous
with an interface. Arpad noted that in VHDL-AMS a "quantity" seems to be what
electrical engineers consider a port.
Arpad reviewed existing use of "port" in [External Model]. He noted that on
page 93 there is the following definition:
port - access point in an [External Model] or [External Circuit]
definition for digital or analog signals
On page 94, in Table 12, A_gnd is defined as "Global reference voltage port",
but the paragraph below the table says, "A_gnd is a universal reference node".
Arpad noted this was a can of worms we would ultimately have to address.
Michael M. agreed that we have an extensive, though likely not technically
difficult, search and replace problem. Radek agreed that this might be a
fairly easy item for the Editorial group to address. Radek said we have to
obey the nomenclature of text books and other references in which a port is
a port, not a simple node. The concept of port has been well established for
many years.
Bob suggested we not deal with this in IBIS 7.0. Arpad agreed in general, but
noted that since we had just changed BIRD158 (replacement BIRD draft) to refer
to the triangle references as the reference "node" A_gnd, we should make the
definition of A_gnd consistent. Arpad suggested we only change:
Table 12: A_gnd - Global reference node. (instead of voltage port)
pg. 94: A_gnd is a global reference node. (instead of universal)
Arpad noted that he understood Bob's concern about changing the table, since
other entries (A_puref, etc.) still used "port", but he felt it was important
to make A_gnd consistent with other sections. Bob said he was okay with
Arpad's two proposed changes.
Arpad asked where these changes should be made, BIRD189 or somewhere else.
Michael M. said they should be handled in BIRD189. The group agreed. Radek
noted that he had proposed some changed to BIRD189 in the multi-lingual
section, and these could be extended to include Arpad's suggested changes.
- Michael M.: Motion to adjourn.
- Curtis: Second.
- Arpad: Thank you all for joining.
AR: Arpad to prepare a new draft of the BIRD to supersede BIRD158.7.
-------------
Next meeting: 10 April 2018 12:00pm PT
-------------
IBIS Interconnect SPICE Wish List:
1) Simulator directives
