Subject: Thoughts on OOMRs
From: Kevin Cameron x3251 (Kevin.Cameron@nsc.com)
Date: Tue Feb 06 2001 - 18:05:38 PST
OOMRs are defined during elaboration. They are essentially
like "undeclared" ports in their target modules - and can
be handled that way as far as semantics go. However, as OOMRs
are often used as "probes" from digital testbenches it is
probably not a good idea to let the target end assume the
default discipline for the target module, as that would
possibly cause an inappropriate A2D converter insertion.
I think we need a syntax for defining a special "probe"
discipline that can be found from the default discipline for
a module so that only a "light weight" A2D is inserted e.g.:
discipline TSMC33_18 probe LOGIC_3_3V; // Use a 3.3V
// logic monitor
Otherwise if there is A/D conversion without considering the
OOMR the OOMR should attach to it's digital output, and after
that it should probably fail.
Using an OOMR to drive an analog net from digital will also
require a (digital) discipline to determine the D2A. I would
take the default from the driving context, and if that is
unsatisfactory we may need to extend the module syntax to
include discipline definition for OOMRs as well as local
nets (a mechanism which could be used for probes too).
Kev.
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