TruthTable < P1076/Ballots

P1076/Ballots Web>Vhdl2019CollectedRequirements>TruthTable (2020-02-17, JimLewis) (raw view)EditAttach
---+ Truth Tables

<br />%TOC%

---++ Proposal Editing Information
   * Who Updates: &lt;Add YourName &gt;, ...
   * Date Proposed:
   * Date Last Updated:
   * Priority:
   * Complexity:
   * Focus:
---++ Requirement Summary

---++ Related Issues: [[http://www.eda-twiki.org/isac/IRs-VHDL-2002/IR2060.txt][ISAC IR-2060]]
<pre>-------------BEGINNING OF IR----------------

VHDL Issue Number:        2060

Language_Version          VHDL-2002
Classification            Language Modeling Enhancement or Deficiency
Summary                   Include truth table for multi-input/multi-output logic.
Relevant_LRM_Sections     
Related_Issues            
Key_Words_and_Phrases     truth table
Authors_Name              J D Russell
Authors_Phone_Number      39-295-4004
Authors_Fax_Number        
Authors_Email_Address     jdrussel@rockwellcollins.com
Authors_Affiliation       
Authors_Address1          
Authors_Address2          
Authors_Address3          

Current Status:           Forwarded

Superseded By:

------------------------
Date Submitted:           26 January 2005
Date Analyzed:
Author of Analysis:
Revision Number:          1
Date Last Revised:        05 February 2005

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

Complex logic functions with numerous inputs (with don't cares), and
numerous outputs (with don't cares), are difficult to express in VHDL.
They are easily expressed compactly with a simple truth table.

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

A syntax similar to that of Altera's AHDL would suffice.  Or something
like this:
    
    table (in1,in2,in3 :in; out1,out2 :out) begin
            0 , - , 1 ,      1  , -   ;
            1 , 1,  0 ,      0  , 0   ;
    end table;
    
    Outputs default to don't care for all inputs not explicitly defined.
    
    
    

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

This should be forwarded to the Modeling and Productivity Group

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

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


-------------END OF IR----------------</pre>
---++ Current Problems / Issues

---++ Use Model / Code Examples

---++ Questions

---++ Proposal

---++ General Comments

Truth tables can be implemented by using constants and array types. Complex lookup tables and ROMs<br />can be defined more easily with functions, which offer conditional statements and loops. The function's<br />result can be stored in a constant to reduce the impact on the performance.

Constants and arrays are already used for the STD_LOGIC operator tables.

So I think the proposed syntax is only syntactic sugar, which might be used by only a handful people.

-- [[Patrick Lehmann][Main.PatrickLehmann]] - 2016-07-28

---++ Non-supporters

-- [[Patrick Lehmann][Main.PatrickLehmann]] - 2016-07-28

---++ Supporters

_Add your signature here to indicate your support for the proposal
Topic revision: r4 - 2020-02-17 - 15:35:00 - JimLewis
P1076/Ballots