{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}


Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
IEEE LANGUAGE REFERENCE MANUAL Std P 1076a -19 9 9 2000/D3 Section Clause 5 77 Copyright © 2000, IEEE. All rights reserved. This is an unapproved IEEE Standards Draft, subject to change. Section Clause 1 5 Specifications This section clause 2 describes specifications , which may be used to associate additional information with a VHDL description. A specification associates additional information with a named entity that has been previously de- clared. There are three kinds of specifications: attribute specifications, configuration specifications, and disconnection specifications. A specification always relates to named entities that already exist; thus a given specification must either follow or (in certain cases) be contained within the declaration of the entity to which it relates. Furthermore, a specification must always appear either immediately within the same declarative part as that in which the declaration of the named entity appears, or (in the case of specifications that relate to design units or the interface objects of design units, subprograms, or block statements) immediately within the declarative part associated with the declaration of the design unit, subprogram body, or block statement. 5.1 Attribute specification An attribute specification associates a user-defined attribute with one or more named entities and defines the value of that attribute for those entities. The attribute specification is said to decorate the named entity. attribute_specification ::= attribute attribute_designator of entity_specification is expression ; entity_specification ::= entity_name_list : entity_class entity_class ::= entity | architecture | configuration | procedure | function | package | type | subtype | constant | signal | variable | component | label | literal | units | group | file entity_name_list ::= entity_designator { , entity_designator } | others | all entity_designator ::= entity_tag [ signature ] entity_tag ::= simple_name | character_literal | operator_symbol 1. To conform to IEEE rules. 2. To conform to IEEE rules.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
IEEE Std P 1076a -1999 2000/D3 IEEE STANDARD VHDL 78 Section Clause 5 Copyright © 2000, IEEE. All rights reserved. This is an unapproved IEEE Standards Draft, subject to change. The attribute designator must denote an attribute. The entity name list identifies those named entities, both im- plicitly and explicitly defined, that inherit the attribute, as described below: If a list of entity designators is supplied, then the attribute specification applies to the named entities denoted by those designators. It is an error if the class of those names is not the same as that denoted by the entity class. If the reserved word others is supplied, then the attribute specification applies to named entities of the specified class that are declared in the immediately enclosing declarative part, provided that each such entity is not explicitly named in the entity name list of a previous attribute specification for the given attribute.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}