[ibis-macro] observations regarding dependency table BIRD 150
- From: <fangyi_rao@xxxxxxxxxxx>
- To: <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 29 Nov 2012 15:59:26 -0700
IBIS Experts;
I'd like to share my observations on dependency table proposed in BIRD 150.
1. Why do we need dependency table? If the dependent variables are model
specific parameters, then these parameter are redundant. They should be
internal to models and resolved inside models. They should not be exposed to
model users in the first place. The only sensible dependent variables are
reserved parameters.
2. The multi-dimensional independent variable syntax is, in my view, too
specialized and not a true multi-dim solution. It only allows interpolation of
the last independent variable column. It may fit one vendor's need, but is too
limited to address general multi-dim dependency.
3. Fundamentally, resolving parameter dependency, even for reserved
parameters, is a job that belongs to models. Asking EDA tools to perform this
task for models is not a good practice and can easily lead to inconsistency
(e.g. round-off and interpolation method) and loss of flexibility, as we
already saw in the multi-dimensional independent variable case. Dependency
relations have too many variations to be standardized within a simple syntax.
It's better to leave them to models. Ad hoc standardization will open doors to
many problems in the future.
4. Resolving parameter dependency can be done much more cleanly and
flexibly by introducing a new AMI function, say AMI_Resolve. In this function
models will resolve and return reserved parameters to simulators. Bit-time,
BAUD rate, corner and model name can be formal input arguments to the function
and there is no need to introduce the confusing "intrinsic parameters".
Regards,
Fangyi
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