InterfaceBundles < P1076

P1076 Web>Vhdl2019CollectedRequirements>Whiteboards>InterfaceWhiteboard>InterfaceBundles (2015-06-15, BrentHahoe) (raw view)EditAttach
---+ Interface Bundle Requirements

   * Interfaces were originally conceived as using the standard *record* type to group various signal types together.

   * A VHDL-AMS requirement extended this concept to include multiple objects (*terminal* and *quantity* objects).

   * Bundles encompassing objects may be of use within standard VHDL particularly when connecting to subprogram parameters.

   * A bundle requires a new object to carry/transport the connection between interface termini, in a similar manner to signals of *record* type were used in the original proposals.

   * The group construct was suggested as a possible method for encapsulating this new object bundling:
      * The *group* object first defines a template of the objects to be grouped together.
      * A *group* then groups together named objects of the class defined by the template.
      * Groups were introduced as a mechanism to apply the same attributes to a number of different objects.
      * Because groups do not specify the types of object classes, they are probably not useful for bndle specification.

   * Specify a *bundle* template:
<sticky><pre><verbatim>
      bundle
         group CPU_bg is 
            signal DATA       : DATA_st;
            signal ADDR       : ADDR_st;
            signal R_W        : Std_Logic;
            signal SLAVE_SEL  : SLAVE_SEL_at;
            signal SLAVE_DATA : SLAVE_DATA_at;

      end group CPU_bg;
</verbatim></pre></sticky>
      * Similar to a *record* type declaration
      * Objects may be of class *signal*, *shared* *variable*, *constant* or *file*
      * VHDL-AMS will add the extra classes of *quantity* and *terminal*

   * An element of a *bundle* template will have a type and an object class associated with it.

   * A *bundle* template will itself be an object class that can be included within another *bundle* template. Bundles then become hierarchical.

   * A *bundle* template can be declared in a package.

   * A *bundle* must be able to be declared as an object in order to connect termini of interfaces, cf. signals.
<sticky><pre><verbatim>
      bundle CPU_b : CPU_bg;
 </verbatim></pre></sticky>
   * A *bundle* template can be declared in an architecture or subprogram.

   * The *bundle* template must be able to be used in a new *modport* construct to specify port/parameter modes individually for its elements.

   * If a *bundle* object contains signals and variables, different parts will update at different delta times.

   * Can bundles be assigned and do we need a new assignment operator for a mixed bundle. Neither "<=" nor ":=" would seem to be appropriate.
Topic revision: r3 - 2015-06-15 - 18:40:21 - BrentHahoe
P1076