VHDL Issue Number:      0117
Classification:         Language Definition Problem
Language Version:       VHDL-87
Summary:                The restrictions on sensitivity lists for processes and
                        for wait statements are different.
Related Issues:         None.
Relevant LRM Sections:  9.2, 8.1
Key Words and Phrases:  Process statement, Sensitivity List, Wait Statement
Current Status:         Closed
1076-1993 Disposition:  Closed (All Issues Completely Addressed)
Disposition Rationale:  Section 9.2 was updated.
Superseded By:          N/A
-----------------------
Date Submitted:         1989/06/21
Author of Submission:   Ken Scott
Author's Affiliation:   Synopsys, Inc.
Author's Post Address:  1098 Alta Avenue
                        Mountain View, CA  94043
Author's Phone Number:  (415) 962-5000
Author's Fax Number:    
Author's Net Address:   kscott@synopsys.com
-----------------------
Date Analyzed:          1990/11/16
Author of Analysis:     Paul Menchini (mench@clsi.com)
Revision Number:        $Revision: 1.10 $
Date Last Revised:      $Date: 1995/08/03 18:43:48 $


Description of Problem
----------------------
In the fourth paragraph of chapter 9.2, the sensitivity list for a process is
restricted in that it only allows static signal names.

In the second paragraph of chapter 8.1, the sensitivity list for a wait
statement's sensitivity clause contains that restriction AND a restriction
which allows only signals 'for which reading is permitted.'


Proposed Resolution
-------------------
The fourth paragraph of chapter 9.2, should be modified to include this
restriction as well, because a process with an explicit sensitivity list is
supposed to be equivalent to a process with a wait statement "...as the last
statement of the process statement part;..."  If a signal were included in the
process's sensitivity list whose value could not be read, then the equivalent
process would not be defined.

VASG-ISAC Analysis & Rationale
------------------------------
The author is correct.


VASG-ISAC Recommendation for IEEE Std 1076-1987
-----------------------------------------------
Impose the restriction that the signals in a process sensitivity list are
static signal names for which reading is permitted.


VASG-ISAC Recommendation for Future Revisions
---------------------------------------------
Incorporated this additional restriction into the language of Section 9.2.
Language revised in IEEE Std 1076-1993 as recommended.
Issue closed.