VHDL Issue Number: 0170 Classification: Language Deficiencies and Modeling Problems Language Version: VHDL-87 Summary: Array attributes should be allowed to be static. Related Issues: 0069 Relevant LRM Sections: 7.4, 14.1 Key Words and Phrases: Array attributes, 'Left, 'Right, 'High, 'Low, 'Range, 'Reverse_Range, 'Length Current Status: Submitted 1076-1993 Disposition: Closed (All Issues Completely Addressed) Disposition Rationale: Section 7.4.1 resolves these issues along the lines outlined in the proposed resolution (See LRS 15). Superseded By: N/A ----------------------- Date Submitted: 1991/03/15 Author of Submission: Paul Menchini Author's Affiliation: CAD Language Systems, Inc. Author's Post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: Author's Net Address: mench@clsi.com ----------------------- Date Analyzed: TBD Author of Analysis: TBD Revision Number: $Revision: 1.7 $ Date Last Revised: $Date: 1995/05/13 19:34:42 $ Description of Problem ---------------------- VHDL models with unconstrained ports can be difficult to write in a general way. Consider an unconstrained, one-dimensional array port, P, of an entity. The name "P(P'Left)" cannot be an actual in a component instance in an architecture corresponding to the entity, because "P'Left" is not globally static. Moreover, consider a signal assignment of the form "S(S'Left) <= ;". The designer's intent is likely to create a single driver for the first element of the signal; however, as "S'Left" is not static, the signal assignment to "S(S'Left)" requires that the enclosing process contain drivers for all of S. Proposed Resolution ------------------- Attribute names involving 'Left, 'Right, 'High, 'Low, 'Range, 'Reverse_Range, and 'Length should be allowed to be globally and locally static, depending on the characteristics of their prefix. In particular, the staticness should not depend on whether the prefix is the name of the array (sub)type or object, it should depend only on whether the bounds and direction of the appropriate index subtype are globally or locally static. This proposed resolution is consistent with the expansive view expressed in the "Recommendation for Future Revisions" section of Issue Report 0069. VASG-ISAC Analysis & Rationale ------------------------------ TBD VASG-ISAC Recommendation for IEEE Std 1076-1987 ----------------------------------------------- TBD VASG-ISAC Recommendation for Future Revisions --------------------------------------------- TBD