VHDL Issue Number:      0125
Classification:         Language Deficiencies and Modeling Problems
Language Version:       VHDL-87
Summary:                Disconnection specification restriction is too strong.
Related Issues:         0040, 0061
Relevant LRM Sections:  5.3
Key Words and Phrases:  Guarded Signals, Disconnection specifications,
                        Declarative Region
Current Status:         ISAC-Approved
1076-1993 Disposition:  Closed (All Issues Completely Addressed)
Disposition Rationale:  LRM updated to be decl part based (sect 5.3)
Superseded By:          N/A
-----------------------
Date Submitted:         1989/06/21
Author of Submission:   Ken Scott
Author's Affiliation:   Vantage Analysis Systems, Inc.
Author's Post Address:  42840 Christy St., Suite 201
                        Fremont, CA   94538
Author's Phone Number:  (415) 659-0901
Author's Fax Number:    
Author's Net Address:   N/A
-----------------------
Date Analyzed:          1990/10/10
Author of Analysis:     Paul J. Menchini (mench@clsi.com)
Revision Number:        $Revision: 1.7 $
Date Last Revised:      $Date: 1995/05/13 19:34:42 $


Description of Problem
----------------------
In Section 5.3, there is a sentence in the 5th from the last paragraph which
states:

       "No guarded signal may be declared in a given declarative
        region following such a disconnection specification."

This restriction is too strong, in that it should be legal to declare a guarded
signal after such a disconnection specification provided that the TYPE of that
guarded signal is not the same.


Proposed Resolution
-------------------
This effect could be achieved by the following modification to that sentence:

       "No guarded signal OF THAT GIVEN TYPE may be declared in a
        declarative region following such a disconnection
        specification."


VASG-ISAC Analysis & Rationale
------------------------------
The author is correct insofar as the statement is overly restrictive.  However,
the entire chapter on specifications suffer a confusion of declarative parts
vs. declarative regions.  This issue was resolved for attribute specification
in Issue Report 40; a recommendation is contained therein to treat
disconnection specifications similarly.


VASG-ISAC Recommendation for IEEE Std 1076-1987
-----------------------------------------------
1.  Treat Section 5.3 as appling to declarative parts, not declarative regions.

2.  Treat the last sentence of Paragraph 3 as applying to disconnection
    specifications of "the given type", in line with the language of the
remainder of the paragraph.


VASG-ISAC Recommendation for Future Revisions
---------------------------------------------
1.  Rewrite Section 5.3 to apply to declarative parts, not declarative regions.

2.  Rewrite the last sentence of Paragraph 3 of Section 5.3 to read:

       "No guarded signal of the given type may be declared in a given
        declarative part following such a disconnection specification."