Mike,
For AMI_Version 6.1 AMI files, the statement below is a Parser BUG because
Reserved_Parameters are illegal under the Model_Specific branch..
“Some people put PAM4 parameters in Model_Specific, where the rules for them
are not checked. But tools should also then ignore them with respect to their
special meanings. Move on with a Range into Reserved_Parameters though, and you
get errors like this from ibischk6:”
We should check this and possibly create a BUG report for this and any other
new V6.1 parameter. The user can always downgrade the AMI_Version number to
legally put the PAM4 modulation parameters under the Model_Specific branch.
Bob
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] ;
On Behalf Of Mike LaBonte
Sent: Wednesday, November 2, 2016 11:20 AM
To: Bob Miller (APD); Curtis Clark
Cc: IBIS-ATM
Subject: [ibis-macro] Re: Draft Format and Usage Out Clarifications BIRD
Some people put PAM4 parameters in Model_Specific, where the rules for them are
not checked. But tools should also then ignore them with respect to their
special meanings. Move on with a Range into Reserved_Parameters though, and you
get errors like this from ibischk6:
E4627 - Illegal Format Range specified for PAM4_UpperThreshold
I have trouble imagining how helpful it would be to allow more formats for Out
parameters. This is weighing the probability that a model will be coded with
incorrect calculations against the probability that the model maker will put
the wrong data in an AMI file. And if there is any complexity to the numerical
space that simple limits on each parameter can’t express, the checks would have
to widen the space and allow some illegal value combinations through. For
example, the ranges for the three PAM4 thresholds .might overlap, so if a model
produces lower values greater than the center value, that might not be flagged
as an error based on AMI setting alone.
Mike
From: Bob Miller (APD) [mailto:bob.miller@xxxxxxxxxxxx] ;
Sent: Tuesday, November 01, 2016 5:57 PM
To: Curtis Clark
Cc: Mike LaBonte; IBIS-ATM
Subject: Re: [ibis-macro] Re: Draft Format and Usage Out Clarifications BIRD
I was recalling my usage from memory; it was actually the threshold
parameters, not the offset parameters which were problematic.
I was doing this in the ami file:
(PAM4_UpperThreshold (Usage Out)(Range 0.33 0.0 1.0)(Type Float)
(Description "The decision level for the upper PAM4 eye")
)
(PAM4_CenterThreshold (Usage Out)(Range 0.0 -1.0 1.0)(Type Float)
(Description "The decision level for the center PAM4 eye")
)
(PAM4_LowerThreshold (Usage Out)(Range -0.33 -1.0 0.0)(Type Float)
(Description "The decision level for the lower PAM4 eye")
)
The EDA tool which did not send these parameters to the model, upon receiving
no values for the threshold parameters from the executable model, quietly used
{0.33,0,-0.33} for the trio. But the intention was for the model to return
these values to the EDA tool based on other hardware tap settings and
adaptation thereof.
Another popular EDA tool (the one I originally regressed the model on) sent
these Usage Out parameters to the model in the parameter string and the model
dutifully returned the real values to the EDA tool.
One could legitimately argue that I "got what I deserved." But perhaps a
little clarification in IBIS-AMI is in order.
Regards,
Bob
On Tue, Nov 1, 2016 at 3:27 PM, Curtis Clark <curtis.clark@xxxxxxxxx> wrote:
My guess is that Bob was referring to the default value that is given in the
spec (0.0) for use when that parameter is not declared in the .ami file at all.
Is that right Bob?
Thanks,
Curtis
On Tue, Nov 1, 2016 at 5:23 PM, Mike LaBonte <mlabonte@xxxxxxxxxx> wrote:
The only allowable data Format for many Reserved_Paramneters including the PAM4
Lower/Center/Upper ones is Value, and Default is illegal for Format Value. So
technically there should have been no Default to use, but there should have
been some kind of Value in the AMI file that a tool could use when the model
does not output it.. However, since IBIS says “For Usage Out, the value in the
AMI parameter leaves are determined by the Algorithmic Model.” (oops,
grammatical error), I don’t think tools should be silent about substituting
anything. Some people put unusable Values like “NA”, attempting to cause a flag
to be thrown on the play if it isn’t replaced.
Mike
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] ;
On Behalf Of Bob Miller (Redacted sender "bob.miller" for DMARC)
Sent: Tuesday, November 01, 2016 5:05 PM
To: Curtis Clark
Cc: dmarc-noreply@xxxxxxxxxxxxx; Walter Katz; Mirmak, Michael; IBIS-ATM
Subject: [ibis-macro] Re: Draft Format and Usage Out Clarifications BIRD
The model maker can specify Usage InOut if that's the behavior they want,
right?
