VHDL Issue Number:      0058
Classification:         Language Definition Problem
Language Version:       VHDL-87
Summary:                Index specification and IF generation should be illegal
Related Issues:         0073
Relevant LRM Sections:  1.3.1
Key Words and Phrases:  Index specification, block configuration, generate
                        statement
Current Status:         ISAC-Approved
1076-1993 Disposition:  Closed (All Issues Completely Addressed)
Disposition Rationale:  The bullets and paragraphs at the end of section 
                        1.3.1 have been augmented to fix these problems.
Superseded By:          N/A
-----------------------
Date Submitted:         1989/02/10
Author of Submission:   Doug Dunlop
Author's Affiliation:   Intermetrics, Inc.
Author's Post Address:  4733 Bethesda Ave #415
                        Bethesda, MD  20814
Author's Phone Number:  (301) 657-3775
Author's Fax Number:    
Author's Net Address:   dunlop@inmet.inmet.com
-----------------------
Date Analyzed:          1990/10/01
Author of Analysis:     Doug Dunlop
Revision Number:        $Revision: 1.6 $
Date Last Revised:      $Date: 1995/05/13 21:53:48 $


Description of Problem
----------------------
LRM 1.3.1 should declare it illegal to use an index
specification in a block specification unless the block configuration
configures a generate statement that uses a FOR generation scheme.


Proposed Resolution
-------------------
We assume this.


VASG-ISAC Analysis & Rationale
------------------------------
The paragraph beginning "For any name that is the label of a generate statement
within a given block, ..." in LRM 1.3.1 seems to be written with the assumption
that the generate statement is iterative rather than conditional (i.e., the
wording assumes the existence of a generate index).  The meaning of a block
configuration on a conditional generate statement does not seem to be defined,
although such a meaning is perhaps "obvious".


VASG-ISAC Recommendation for IEEE Std 1076-1987
-----------------------------------------------
The semantics of a block configuration on a conditional generate statement
should be clarified as follows:

  (1) At most one block configuration may correspond to a conditional generate
      statement.

  (2) Such a block configuration applies to the (potential) implicit block
      generated by the generate statement.

  (3) No index specification is allowed on such a block configuration.


VASG-ISAC Recommendation for Future Revisions
---------------------------------------------
LRM 1.3.1 badly needs to be re-worked.  The ISAC has heard that users have
a very difficult time with the section.  Refer also to IR-0073.