VHDL Issue Number:      2014

Language_Version:       VHDL-2002
Classification:         Language Modeling Enhancement or Deficiency
Summary:                Allowance of the keyword "all" in place of a sensitivity list is desirable
Relevant_LRM_Sections:  8.1 Wait Statement 9.2 Process Statement
Related_Issues:
Key_Words_and_Phrases:  sensitivity list
Authors_Name:           Geoff Bull
Authors_Phone_Number:   +61 2 48711254
Authors_Fax_Number:     +61 2 48711465
Authors_Email_Address:  gbull@acenet.com.au
Authors_Affiliation:    none
Authors_Address1:       PO Box 1172
Authors_Address2:       Bowral NSW 2575
Authors_Address3:       Australia

Current Status:         Forwarded

Superseded By:

------------------------
Date Submitted:         22 April 2002
Date Analyzed:          29-Oct-04
Author of Analysis:     Peter Ashenden
Revision Number:        1
Date Last Revised:      03-December-2004

Description of Problem
----------------------

    When designing logic for synchronous circuits (e.g. rtl for asics)
    typically processes are used in just two ways 1. the sensitivity
    list contains just one signal, namely the clock.  2. the
    sensitivity list contains all input signals to the process

    The second case is used to define unclocked logic.  Unfortunately,
    it is frequently the case that the user accidentally omits a signal
    from the sensitivity list and an unwanted latch is inferred. This
    problem can be difficult to debug.  In addition, sensitivity lists
    present a code maintenance overhead - after modifying the logic
    for a process, the sensitivity list must be carefully checked.
    just one sign


Proposed Resolution
-------------------

    that it should be permitted to use the keyword "all" as a
    sensitivity list.  This would mean that the process is sensitive
    to all the signals used as inputs to the process.

VASG-ISAC Analysis & Rationale
------------------------------

The VHDL-200x Fast Track group is addressing this enhancement request
as part of FT-19.


VASG-ISAC Recommendation for IEEE Std 1076-2002
-----------------------------------------------

No change.


VASG-ISAC Recommendation for Future Revisions
---------------------------------------------

Implement extensions developed in FT-19.


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