[vhdl-200x-ft] FT27: optional architectures

Folks,

Proposal FT27 specifies that architecture bodies be optional for design
entities, and that entities can include arbitrary block declarations and
statements. However, the proposal does not say how to revise configuration
declarations to take account of the changes to entities and architectures.

Currently, a configuration declaration includes block configurations that
name architecture bodies. Such a block configuration represents the
external block denoted by a design entity, either one identified by the
configuration declaration or one bound to a component instance.

With the proposed change, an external block may be denoted by an entity
alone. We need to provide a way of specifying in a binding indication that
no architecture body be used (even if there is one available), and a way of
specifying a block configuration for the denoted external block.

My suggestion is to use the reserved word "open" in place of an architecture
name. Thus, the syntax rule for block_specification in page 13 would be
revised to:

  block_specification ::=
      architecture_name
    | open
    | block_statement_label
    | generate_statement_label [ ( index_specification ) ]

Also, the syntax rule for entity_aspect on page 81 would be revised to:

  entity_aspect ::=
      entity entity_name [ ( architecture_identifier | open ) ]
    | configuration configuration_name
    | open

I'd also suggest revising the default binding rules to specify that the
architecture to use is the most recently analyzed, if one exists, or none
otherwise; and that the rule specifying that it be an error if no
architecture exists be deleted.

Comments?

Cheers,

PA

--
Dr. Peter J. Ashenden                        peter@ashenden.com.au
Ashenden Designs Pty. Ltd.                   www.ashenden.com.au
PO Box 640                                   Ph:  +61 8 8339 7532
Stirling, SA 5152                            Fax: +61 8 8339 2616
Australia                                    Mobile: +61 414 70 9106