From: Steven Sharp (sharp@cadence.com)
Date: Mon Oct 15 2001 - 13:25:06 PDT
Precedence: bulk
Short answer: the standard is wrong.
The 1995 standard was supposed to match XL, but does not describe port
collapsing. Note that port collapsing is done at the discretion of the
tool. Whether it is done is affected by too many complex and tool-specific
factors to be specified in a standard. Perhaps this is why it was omitted.
It would have been better to have specified that collapsing is allowed.
The standard does make a sort of reference to collapsing. It states that
if a port direction has been declared with a direction that does not match
the actual direction, it may be coerced to inout. If it is not coerced, a
warning must be issued. Coercing to inout is the effective result of port
collapsing. This is actually a poor attempt to describe port collapsing.
This is in section 12.3.6 in the 1995 standard.
Steven Sharp
sharp@cadence.com
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