Minutes from the 26 Jul 2016 ibis-atm meeting are attached.
Mike
IBIS Macromodel Task Group
Meeting date: 26 July 2016
Members (asterisk for those attending):
ANSYS: Dan Dvorscak
Curtis Clark
Broadcom (Avago): Xingdong Dai
* Bob Miller
Cadence Design Systems: Ambrish Varma
Brad Brim
Kumar Keshavan
Ken Willis
Cisco: Seungyong (Brian) Baek
eASIC: * David Banas
Marc Kowalski
Ericsson: Anders Ekholm
GlobalFoundries: Steve Parker
IBM * Luis Armenta
Intel: * Michael Mirmak
Keysight Technologies: * Fangyi Rao
* Radek Biernacki
Ming Yan
Maxim Integrated Products: Hassan Rafat
Mentor Graphics: John Angulo
* Arpad Muranyi
Micron Technology: * Randy Wolff
Justin Butterfield
QLogic Corp.: James Zhou
Andy Joy
SiSoft: * Walter Katz
Todd Westerhoff
* Mike LaBonte
Synopsys: Rita Horner
Kevin Li
Teraspeed Consulting Group: Scott McMorrow
Teraspeed Labs: * Bob Ross
TI: Alfred Chong
The meeting was led by Arpad Muranyi.
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Opens:
- None.
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Review of ARs:
- Randy send C_comp presentation to Mike for posting
- Done
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Call for patent disclosure:
- None.
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Review of Meeting Minutes:
- None were available to review.
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New Discussion:
Next Steps
- Arpad: Are there any new agenda items or existing ones that should be higher
priority?
- Walter: I assembled a list of what should go into IBIS 6.2.
- None of the items are yet approved.
- Bob said we need to have some number of BIRDs to be approved.
- We think we know what those BIRDs are.
- Arpad: What are these BIRDs?
- Walter: The list is not readily available now.
- Mike: I intend to send a document about this by Friday.
AR: Mike produce list of candidate BIRDs to write for IBIS 6.2
6) IO Buffer Reference Terminals
- Walter: What we were calling Device In Action is now Device In Simulation.
- When the simulation rail voltage is different from that tested it gets
complex.
- For drivers, power aware simulation adds more complexity.
- Return path is another issue, that we probably can't deal with. The model
maker must get that right.
- IBIS can't say how to scale when the rail to rail voltage difference is not
what was measured.
- Bob: I support that. We should have a generic statement like the one Michael
Mirmak proposed, and then Walter tuned.
- Walter: We discussed IEEE P370 by email.
- In their system an upside down diamond symbol was signal ground, a local
ground.
- The other symbols in P370 are earth and chassis grounds.
- The IEEE people agree their wording could be cleaned up.
- We should use the signal ground symbol in IBIS 6.2.
- I will circulate their new text when they have an update.
- Arpad: We should have a written definition of the meaning of their symbol.
- Are all of those die grounds shorted together?
- Radek: The implication is that they are shorted.
- Agree we could use that symbol, replacing "GND" in our figures.
- Walter: We need to put words around it.
- Arpad: There is a disconnect.
- V/T tables are measured from the test fixture ground to the signal.
- The IBIS model may not have that ground if there is no 0 voltage terminal.
- In that case the measured voltages are shifted from anything that can be
measured.
- Radek: We have the [* Reference] keywords for that, to give terminal
voltages relative to the unavailable reference.
- Arpad: Those are referenced to the test fixture ground.
- Walter: Test fixture ground may not be a pin on the component.
- A voltage is supplied to each rail from that reference node.
- A trace on a plane layer must be imaged to some rail attached to package.
- Arpad: For a bouncing device the question is what does the V/T table voltage
mean?
- Bob: V_Fixture is also referenced to local ground, which we assume is perfect.
- Rising and Falling waveforms are also relative to that local ground.
- The waveform is transformed by K table using the reference node.
- In simulation the reference nodes can be modulated.
- I don't envision recalculating K tables based on a changing voltage.
- The IV tables however are referenced to the changing voltage.
- Radek: Without V/T tables we calculate simple K table multipliers.
- But we do have V/T tables, so we should accommodate that.
- Bob: The V/T is used once under static conditions.
- Walter: I once wrote a simulator that finds the K/T function under fixed
supply conditions, then it just runs it as calculated.
- Arpad: We can expect a few related BIRDs to be written and reviewed in this
group.
- Walter moved to remove his item 6 "IO Buffer Reference Terminal proposal"
from the weekly agenda.
- There was some discussion about this:
- Radek: There is useful information here.
- Walter: But we are limited to using just the buffer terminals.
- The reference point is not always a buffer terminal.
- Radek: But the reference exists somewhere.
- It may be the same pin used for [Pulldown Reference], for example.
- Walter: An input has just three terminals.
- Arpad: I agree with Walter.
- Radek: This is more of an issue for the driver.
- Walter: I/V table current is a function only of the difference between I/O
and
reference terminals.
- Radek: Where is the local ground?
- Arpad: That doesn't matter.
- Radek: We need to answer the question of which terminal the I/O driving
against.
- Mike: We seem to have part of the answer to how to supply buffers but not
all of it.
- Having started the discussion and feeling we understand it as well as we
can, we should not now decide that the specification needs no change.
- Other people will need to understand this.
- Arpad: An example mother board might have a ground plane and 2 supply
planes, +2.5V and -2.5V.
- How do you get a connection to the 0v ground plane?
- The tool will connect a complete circuit, and once the connection is
completed
you know the reference point.
- That reference cannot be defined by the buffer, it doesn't know how it's
connected.
- Radek: We must know what to measure against.
- Walter: It is measured relative to the rails that supply the device.
- You can't reference against a node that's not on the chip.
- Bob: Note that this discussion is about the Pin_Reference keyword, listed
further down on the agenda.
- Bob seconded the motion.
- With no objection the motion passed.
- Arpad: We look forward to agenda recommendations from the editorial group.
- Arpad: Thank you all for joining.
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Next meeting: 2 August 2016 12:00pm PT
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IBIS Interconnect SPICE Wish List:
1) Simulator directives
