From: Clifford E. Cummings (cliffc@sunburst-design.com)
Date: Wed Oct 03 2001 - 14:05:21 PDT
Precedence: bulk
Dear BTF -
While submitting typo corrections to the IEEE, I would also like to try to
submit one clarification paragraph in the list. The clarification paragraph
has to do with implicit nets and the wording was submitted by Paul Graham
of Cadence.
PROPOSAL: Add the following indented paragraph to the end of section 3.5.
Indenting to match the indenting of the two last paragraphs already in
section 3.5:
"If an identifier appears as the target of a continuous assignment
statement, and that identifier has not been declared previously, then an
implicit scalar wire declaration is assumed for that identifier."
Please vote YES or NO on the above proposed addition to the end of section
3.5 and e-mail your vote to me no later than Monday, October 15th, 2001.
<p><p>I know I said we could not add any clarification to the IEEE document, but
I believe this is an exception for the following reasons:
(1) Verilog-1995 required the target of a continuous assignment that did
not drive a port to be explicitly declared.
(2) Verilog-2001 removes this non-orthogonal restriction. As Mike MacNamara
has noted, the BTF tried to remove the restriction by changing the first
paragraph in section 6.1.2 to read as follows:
"The continuous assignment statement shall place a continuous assignment on
a net data type. The net may be explicitly declared, or may inherit an
implicit declaration in accordance with the implicit declarations rules
defined in 3.5."
This was not clear enough as to our intent.
(3) As has been noted in earlier threads, Don Mills & Stu Sutherland
authored a paper about the Verilog-2001 Standard that incorrectly described
the behavior of this change. This paper has been widely distributed
(SNUG2001-Europe, SNUG2001-San Jose, SNUG2001-Dallas, others?) and used by
many as a brief authoritative tutorial about Verilog-2001 enhancements.
Although the paper has been updated, corrected and placed on Don Mills' web
site, the damage has been done, which is why I think we need to be more
explicit in this description in the published IEEE1364-2001 Standard and
not hope that we can verbally correct the confusion as the questions arise.
We should be able to say: "This enhancement is described at the end of
section 3.5 of the IEEE1364-2001 Standard."
Please e-mail me your vote!
Regards - Cliff Cummings
Behavioral Task Force Chairperson
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