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---+!! Interfaces LCS/Proposal Notes

 %TOC%

---++ View Structure
Views give mode control to composite <b>type</b> objects declared in interface lists
of entity structures.

Views have a slightly altered syntax, dependant on whether they apply to a
<b>record</b> <b>type</b> or an <b>array</b> <b>type</b>.

---+++ Record View

Given a <b>record</b> <b>type</b> - 'MyRecordType':

<sticky><pre>%BLACK%
<b>type</b> MyRecordType <b>is</b>
   <b>record</b>
      ElementA : ElementAType;
      ElementB : ElementBType;
      ElementC : ElementCType;
      ElementD,
      ElementE,
      ElementF : ElementDEFType;
   <b>end</b> <b>record</b> MyRecordType;
</pre></sticky>

A <b>view</b> (!MyRecordView) defining a particular mode definition for a given
interface object of <b>record</b> <b>type</b> 'MyRecordType':

<sticky><pre>%BLACK%
<b>view</b> MyRecordView <b>of</b> MyRecordType <b>is</b>
   <b>record</b>
      ElementA : ElementAMode;
      ElementB : ElementBMode;
      ElementC : ElementCMode;
      ElementD,
      ElementE,
      ElementF : ElementDEFMode;
   <b>end</b> <b>record</b> <b>view</b> MyRecordView;
</pre></sticky>


---+++ Array View

Given an <b>array</b> <b>type</b> - 'MyArrayType':

<sticky><pre>%BLACK%
<b>type</b> MyArrayType <b>is</b>
   <b>array</b>(
      <b>of</b> ElementType;
</pre></sticky>

A <b>view</b> (!MyArrayView) defining a particular mode definition for a given
interface object of <b>record</b> <b>type</b> 'MyArrayType':

<sticky><pre>%BLACK%
<b>view</b> MyArrayView <b>of</b> MyArrayType <b>is</b>
   <b>array</b>(
      TypeRangeZ : TypeRangeZMode,
      TypeRangeY : TypeRangeYMode,
      TypeRangeX : TypeRangeXMode)
   <b>end</b> <b>array</b> <b>view</b> MyArrayView;
</pre></sticky>


---+++ Examples

Some general examples of usage.

Bottom level is a general peripheral interface:

<sticky><pre>%BLACK%
<b>type</b> MyPeripheralType <b>is</b>
   <b>record</b>
      Select     : Std_uLogic;
      Enable     : Std_uLogic;
      Read_Write : Std_uLogic;
      ReadData   : Std_uLogic_Vector(31 downto 0);
      WriteData  : Std_uLogic_Vector(31 downto 0);
   <b>end</b> <b>record</b> MyPeripheralType;
</pre></sticky>

<sticky><pre>%BLACK%
<b>view</b> MyPeripheralView <b>of</b> MyPeripheralType <b>is</b>
   <b>record</b>
      Select     : <b>in</b>;
      Enable     : <b>in</b>;
      Read_Write : <b>in</b>;
      ReadData   : <b>in</b>;
      WriteData  : <b>out</b>;
end <b>record</b> <b>view</b> MyPeripheralView;
</pre></sticky>

One peripheral interface is then mapped into an <b>array</b> of many
peripheral interfaces. The new mode *null* is used to disconnect all other
peripheral interfaces and allow one to be connected using a generic value:

<sticky><pre>%BLACK%
<b>type</b> MyInterfaceType <b>is</b>
   <b>array</b>(50 downto 1)
      <b>of</b> MyPeripheralType;
</pre></sticky>

<sticky><pre>%BLACK%
<b>view</b> MyInterfaceView <b>of</b> MyInterfaceType <b>is</b>
   <b>generic</b>(
      <b>constant</b> value_g : Positive);
   <b>array</b>(
      50      : <b>in</b>,
      value_g : <b>view</b> MyPeripheralView,
      others  : <b>null</b>);
   <b>end</b> <b>array</b> <b>view</b> MyInterfaceView;
</pre></sticky>
The top level adds in interface clock and reset:

<sticky><pre>%BLACK%
<b>type</b> MyTopBusType <b>is</b>
   <b>record</b>
      Reset       : Std_uLogic;
      Clock       : Std_uLogic;
      MyInterface : MyInterfaceType;
   <b>end</b> <b>record</b> MyTopBusType;
</pre></sticky>

<sticky><pre>%BLACK%
<b>view</b> MyTopBusView <b>of</b> MyTopBusType <b>is</b>
   <b>generic</b>(
      <b>constant</b> item_g : Positive)
   <b>record</b>
      Reset       : <b>in</b>;
      Clock       : <b>in</b>;
      MyInterface : <b>view</b> MyInterfaceView(value_g => item_g);
end <b>record</b> <b>view</b> MyTopBusView;
</pre></sticky>

---++ Bundles

We need <b>bundle</b> objects to provide interconnect and *bundle* interface
objects to define entity structure interfaces.

With a normal object we have:

object_class object_name : subtype indication ;

e.g.

<b>signal</b> !MySignal : Natural ;

We need a similar syntax for a <b>bundle</b>:

<b>bundle</b> !MyBundle : ????? ;

The association with a <b>bundle</b> is not a <b>type</b> because it has a composite
object structure, so let's call it a  <b>group</b> <b>type</b>. The only valid
format for this(???) is <b>record</b> based:

<sticky><pre>%BLACK%
<b>group</b> <b>type</b> MyGrype <b>is</b>
   <b>record</b>
      <b>signal</b>      ElementA : ElementAType;
      <b>signal</b>      ElementB : ElementBType;
      <b>shared</b>
         <b>variable</b> ElementC : ElementCType;
      <b>signal</b>      ElementD,
      <b>signal</b>      ElementE,
      <b>signal</b>      ElementF : ElementDEFType;
   <b>end</b> <b>record</b> MyGrype;
</pre></sticky>

A <b>bundle</b> can only be declared in a concurrent code region?

But what about passing into a subprogram. Then we may want variables and
constant classes in the <b>bundle</b> <b>group</b> <b>type</b> as well.

This may imply a <b>view</b> of a <b>group</b> <b>type</b> should be able to
modify the object class structure??

A <b>bundle</b> of <b>signal</b> declarations may need to be passed into a <b>function</b>
as a <b>bundle</b> of <b>constant</b> declarations.
Topic revision: r5 - 2016-12-29 - 17:13:31 - BrentHahoe
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