VHDL Issue Number:      1039
Classification:         Language Definition Problem
Language Version:       VHDL-93
Summary:                May subelements and slices of procedure signal
                        parameters be individually driven?
Related Issues:         0209, 0153
Relevant LRM Sections:  8.3.1
Key Words and Phrases:  Drivers, signal parameters
Current Status:         Submitted
1076-1993 Disposition:  N/A
Disposition Rationale:  N/A
Superseded By:          N/A
-----------------------
Date Submitted:         1991/03/18
Author of Submission:   Paul Menchini (edited by Bill Paulsen)
Author's Affiliation:   CAD Language Systems, Inc.
Author's Post Address:  P.O. Box 13036
                        Research Triangle Park, NC  27709-3036
Author's Phone Number:  (919) 361-1913
Author's Fax Number:    N/A
Author's Net Address:   mench@clsi.com
-----------------------
Date Analyzed:          TBD
Author of Analysis:     TBD
Revision Number:        $Revision: 1.6 $
Date Last Revised:      $Date: 1995/05/15 21:26:37 $


Description of Problem
----------------------
(This IR supersedes IR 0209.)

Paragraph 10 (the final paragraph before the note) of Section 8.3.1 (on page
8-5) states:

        If a given procedure is declared by a declarative item that is
        not contained within a process statement, and a signal
        assignment statement appears in that procedure, then the target
        of the assignment statement must be a formal parameter of the
        given procedure or of a parent of that procedure, or an
        aggregate of such formal parameters.

The intent of this paragraph is to ensure that the drivers of all signals can
be statically identified by disallowing global signals from being driven from a
procedure whose body is not defined within a process.

The paragraph is too restrictive given this purpose.  The subelements and
slices of a formal parameter of the procedure (or its parents) should also be
allowed.  Relaxing these restrictions does not prohibit the static
identification of all drivers.


Proposed Resolution
-------------------
Change the quoted paragraph to read:

        If a given procedure is declared by a declarative item that is
        not contained within a process statement, and a signal
        assignment statement appears in that procedure, then the target
        of the assignment statement must be either

            1.  a formal parameter of the given procedure or of a parent
                of that procedure,

            2.  a subelement of a formal parameter of the given
                procedure or of a parent of that procedure,

            3.  a slice of either items 1 or 2, or

            4.  an aggregate consisting entirely of items 1, 2, 3, or 4.

(Item 4 is recursive in anticipation of a favorable response to Issue Report
0153.)


VASG-ISAC Analysis & Rationale
------------------------------
TBD


VASG-ISAC Recommendation for IEEE Std 1076-1993
-----------------------------------------------
TBD


VASG-ISAC Recommendation for Future Revisions
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TBD