400 lines
15 KiB
ReStructuredText
400 lines
15 KiB
ReStructuredText
.. -*- Mode: rst -*-
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.. include:: ../etc/definitions.rst
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.. include:: ./definitions.rst
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6. Making a hierarchical Cell -- Netlist
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========================================
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To illustrate the topic, we will build the netlist of a fulladder from
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standard cell.
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|fulladder_1|
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6.1 Creating an Instance_
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~~~~~~~~~~~~~~~~~~~~~~~~~
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Creating an Instance_ is straigthforward, the constructor needs only three
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parameters:
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#. The Cell_ **into which** the instance is to be created.
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#. The name of the instance.
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#. The **master cell**, the Cell_ model it refers to. The master cell
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will be part of the hierarchical level just below the ``fulladder``
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cell.
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.. note:: Do not confuse the cell the instance is create into (``fulladder``)
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and the cells it refers to (the *master cell* ``xr2_x2``).
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.. code-block:: Python
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af = AllianceFramework.get()
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xr2_x2 = af.getCell( 'xr2_x1', Catalog.State.Views )
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fulladder = af.createCell( 'fulladder' )
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xr2_1 = Instance.create( fulladder, 'xr2_1', xr2_x2 )
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6.2 Creating Nets and connecting to Instances
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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An Instance_ as one Plug_ for each external net of the *master cell*.
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The plug allows to create a **logical** connection bewteen a Net_ of
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``fulladder`` and a net from an Instance_ *master cell*.
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A plug is somewhat equivalent to an *instance terminal* in other
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well known databases.
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Therefore, a plug is related to two nets:
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#. The net of the *master cell* it is linked to. Obviously that
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net cannot be changed. You can access the master net with the
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function ``plug.getMasterNet()``.
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#. The net of ``fulladder`` the plug is connected to. This can
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be set, it is how we build the netlist. To set the net, use
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the function ``plug.setNet( net )``. If the argument is ``None``,
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the plug is *disconnected*.
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To find the plug of an instance associated to a given net in
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the *master cell*, use ``instance.getPlug( masterNet )``.
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The ``masterNet`` argument being an object of class net (not
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its name).
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Building the :cb:`a` net of ``fulladder``:
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.. code-block:: Python
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a = Net.create( fulladder, "a" )
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a.setExternal( True )
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xr2_1.getPlug( xr2_x2.getNet("i0") ).setNet( a )
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a2_1 .getPlug( a2_x2.getNet("i0") ).setNet( a )
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.. note:: **Limitation of Hurricane Netlists.** There is no explicit
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terminal object in the |Hurricane| database. Plugs are
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generated *on the fly* for each *external net* of the
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instance. One important consequence is that a *net*
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cannot appear on the interface as two differently named
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terminals (sometimes referred as *weekly connected*
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terminals). There is a strict bijection between external
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nets and plugs.
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While it may be restrictive, it enforces cleaner designs
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and make it possible for the HyperNet_ concept/class.
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6.3 Power supplies special case
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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For supplies, it may be tedious to connect the Plugs_ of each cell one by one
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(and create a lot of uneeded objects). To avoid that, we may use **Named
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connections**. If a signal in ``fulladder`` is set to *global*, then it will
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be considered as connected to any signal with the *same name* and *global* in
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the master cell of the instances.
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.. code-block:: Python
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vdd = Net.create( fulladder, "vdd" )
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vdd.setExternal( True )
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vdd.setGlobal ( True ) # Will be connected to all the instances.
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6.4 Creating the physical view of a Cell netlist
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Even if loaded in the viewer, an Instance will not be displayed
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until it is placed.
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6.4.1 Transformation
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--------------------
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To place an Instance, we apply a Transformation_ to the coordinate system
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of the *master cell*. A transformation is composed of two operations:
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#. An Orientation_, which can be a symmetry or a rotation (or a combination
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of those two). The Orientation **is applied first** to the coordinate
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system of the *master cell*. The complete list of Orientation and their
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codes are given on the Orientation documentation page.
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#. A **Translation**, applied in second. Translation are represented by
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Points_.
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The transformation is a change of coordinate system, be aware that if the
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abutment box lower left corner of the *master* cell is **not** at ``(0,0)``
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the result of the Transformation may not be what you expect. To simplify
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the computation of the transformation of an instance, always place the
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lower left corner of the abutment box at ``(0,0)``
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6.4.2 Placing an Instance
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-------------------------
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Assuming that we want to place the cells of the ``fulladder`` into two rows,
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that the abutment box lower left corner is at ``(0,0)`` (same for the
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``xr2_x2`` *master cell* layout). Here is the code to place the ``xr2_1``
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instance to left of the second row.
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Setting the translation on an Instance_ is not enough to make it be displayed,
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we also must set its *placement status* to ``Instance.PlacementStatus.PLACED``.
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.. code-block:: Python
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xr2_1.setTransformation( Transformation( DbU.fromLambda( 0.0)
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, DbU.fromLambda(100.0)
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, Transformation.Orientation.MY ) )
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xr2_1.setPlacementStatus( Instance.PlacementStatus.PLACED )
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6.4.3 Nets -- From Plugs to RoutingPads
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---------------------------------------
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As was stated before, Plugs_ represent a logical connection between two
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levels of hierarchy. To make the physical connection to the *master net*
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in the instance, we now must create, in the ``fulladder``, a special
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component which is a kind of *reference* to a component of the
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*master net* (in the master cell).
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The so called *special component* is a RoutingPad_.
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The ``RoutingPad`` can be considered as an equivalent to ``pin`` in other
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well known databases.
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.. code-block:: Python
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rp = RoutingPad.create( a
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, Occurrence( xr2_1.getPlug( xr2_x2.getNet("i0")) )
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, RoutingPad.BiggestArea )
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For the second parameter, we must pass an Occurrence_. Occurrence objects will
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be explained in detail later, for now, let say that we must construct the
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Occurrence object with one parameter : the Plug_ for which we want to create a
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physical connection.
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The RoutingPad_ ``rp`` will be a component of the ``a`` net.
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The third argument ask the constructor of the RoutingPad_ to select in the
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master net, the component which has the biggest area.
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.. note:: **Component selection.** Not all the components of a net can be
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selected for connection through a RoutingPad_. The candidates must
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have been flagged with the NetExternalComponents_ class.
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See `3.6.3 Creating a Component`_.
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6.4.4 Nets -- Regular wiring
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----------------------------
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After the creation of the RoutingPads_, the wiring is to be created with
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ordinary layout components (Horizontal_, Vertical_ and Contact_ possibly
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articulated). Here is the complete code for net ``a``. We made an articulated
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layout where contacts are created over RoutingPads_ then segments over
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contacts.
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.. code-block:: Python
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# Build wiring for a.
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# Create RoutingPads first.
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rp1 = RoutingPad.create( a
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, Occurrence( xr2_1.getPlug( xr2_x2.getNet("i0")) )
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, RoutingPad.BiggestArea )
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rp2 = RoutingPad.create( a
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, Occurrence( a2_1.getPlug( a2_x2.getNet("i0")) )
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, RoutingPad.BiggestArea )
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# Then regular wiring.
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contact1 = Contact.create( rp1, via12, toDbU( 0.0), toDbU(-15.0) )
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contact2 = Contact.create( rp2, via12, toDbU( 0.0), toDbU( 10.0) )
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turn = Contact.create( a , via23, toDbU(10.0), toDbU( 35.0) )
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Horizontal.create( contact2, turn , metal2, toDbU(35.0), toDbU(2.0) )
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Vertical .create( turn , contact1 , metal3, toDbU(10.0), toDbU(2.0) )
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.. note:: In order to better see the layout of the wiring only, open the
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``Controller`` and in the :fboxtt:`Filter` tab, uncheck
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:fboxtt:`Process Terminal Cells`.
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6.5 The Complete Example File
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The example file ``fulladder.py`` can be found in the ``share/doc/coriolis2/examples/scripts/``
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directory (under the the root of the |Coriolis| installation).
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.. code-block:: Python
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#!/usr/bin/python
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import sys
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from Hurricane import *
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from CRL import *
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def toDbU ( l ): return DbU.fromLambda(l)
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def doBreak ( level, message ):
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UpdateSession.close()
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Breakpoint.stop( level, message )
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UpdateSession.open()
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def buildFulladder ( editor ):
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# Get the Framework and all the master cells.
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af = AllianceFramework.get()
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xr2_x2 = af.getCell( 'xr2_x1', Catalog.State.Views )
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a2_x2 = af.getCell( 'a2_x2' , Catalog.State.Views )
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o2_x2 = af.getCell( 'o2_x2' , Catalog.State.Views )
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UpdateSession.open()
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fulladder = af.createCell( 'fulladder' )
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fulladder.setAbutmentBox( Box( toDbU(0.0), toDbU(0.0), toDbU(90.0), toDbU(100.0) ) )
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if editor:
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UpdateSession.close()
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editor.setCell( fulladder )
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editor.fit()
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UpdateSession.open()
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# Create Instances.
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a2_1 = Instance.create( fulladder, 'a2_1', a2_x2 )
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a2_2 = Instance.create( fulladder, 'a2_2', a2_x2 )
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xr2_1 = Instance.create( fulladder, 'xr2_1', xr2_x2 )
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xr2_2 = Instance.create( fulladder, 'xr2_2', xr2_x2 )
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o2_1 = Instance.create( fulladder, 'o2_1', o2_x2 )
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# Create Nets.
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vss = Net.create( fulladder, "vss" )
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vss.setExternal( True )
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vss.setGlobal ( True )
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vdd = Net.create( fulladder, "vdd" )
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vdd.setExternal( True )
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vdd.setGlobal ( True )
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cin = Net.create( fulladder, "cin" )
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cin.setExternal( True )
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xr2_2.getPlug( xr2_x2.getNet('i0') ).setNet( cin )
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a2_2 .getPlug( a2_x2.getNet('i0') ).setNet( cin )
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a = Net.create( fulladder, 'a' )
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a.setExternal( True )
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xr2_1.getPlug( xr2_x2.getNet('i0') ).setNet( a )
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a2_1 .getPlug( a2_x2.getNet('i0') ).setNet( a )
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b = Net.create( fulladder, 'b' )
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b.setExternal( True )
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xr2_1.getPlug( xr2_x2.getNet('i1') ).setNet( b )
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a2_1 .getPlug( a2_x2.getNet('i1') ).setNet( b )
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sout_1 = Net.create( fulladder, 'sout_1' )
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xr2_1.getPlug( xr2_x2.getNet('q' ) ).setNet( sout_1 )
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xr2_2.getPlug( xr2_x2.getNet('i1') ).setNet( sout_1 )
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a2_2 .getPlug( a2_x2.getNet('i1') ).setNet( sout_1 )
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carry_1 = Net.create( fulladder, 'carry_1' )
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a2_1.getPlug( a2_x2.getNet('q' ) ).setNet( carry_1 )
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o2_1.getPlug( o2_x2.getNet('i1') ).setNet( carry_1 )
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carry_2 = Net.create( fulladder, 'carry_2' )
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a2_2.getPlug( a2_x2.getNet('q' ) ).setNet( carry_2 )
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o2_1.getPlug( o2_x2.getNet('i0') ).setNet( carry_2 )
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sout = Net.create( fulladder, 'sout' )
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sout.setExternal( True )
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xr2_2.getPlug( xr2_x2.getNet('q') ).setNet( sout )
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cout = Net.create( fulladder, 'cout' )
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cout.setExternal( True )
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o2_1.getPlug( o2_x2.getNet('q') ).setNet( cout )
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# Instances placement.
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a2_1.setTransformation( Transformation( toDbU(0.0)
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, toDbU(0.0)
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, Transformation.Orientation.ID ) )
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a2_1.setPlacementStatus( Instance.PlacementStatus.PLACED )
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doBreak( 1, 'Placed a2_1' )
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xr2_1.setTransformation( Transformation( toDbU( 0.0)
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, toDbU(100.0)
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, Transformation.Orientation.MY ) )
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xr2_1.setPlacementStatus( Instance.PlacementStatus.PLACED )
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doBreak( 1, 'Placed xr2_1' )
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a2_2.setTransformation( Transformation( toDbU(25.0)
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, toDbU( 0.0)
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, Transformation.Orientation.ID ) )
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a2_2.setPlacementStatus( Instance.PlacementStatus.PLACED )
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doBreak( 1, 'Placed a2_2' )
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xr2_2.setTransformation( Transformation( toDbU( 45.0)
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, toDbU(100.0)
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, Transformation.Orientation.MY ) )
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xr2_2.setPlacementStatus( Instance.PlacementStatus.PLACED )
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doBreak( 1, 'Placed xr2_2' )
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o2_1.setTransformation( Transformation( toDbU(65.0)
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, toDbU( 0.0)
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, Transformation.Orientation.ID ) )
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o2_1.setPlacementStatus( Instance.PlacementStatus.PLACED )
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doBreak( 1, 'Placed o2_1' )
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# Add filler cells.
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tie_x0 = af.getCell( 'tie_x0', Catalog.State.Views )
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rowend_x0 = af.getCell( 'rowend_x0', Catalog.State.Views )
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filler_1 = Instance.create( fulladder, 'filler_1', tie_x0 )
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filler_2 = Instance.create( fulladder, 'filler_2', rowend_x0 )
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filler_1.setTransformation( Transformation( toDbU(50.0)
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, toDbU( 0.0)
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, Transformation.Orientation.ID ) )
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filler_1.setPlacementStatus( Instance.PlacementStatus.PLACED )
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filler_2.setTransformation( Transformation( toDbU(60.0)
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, toDbU( 0.0)
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, Transformation.Orientation.ID ) )
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filler_2.setPlacementStatus( Instance.PlacementStatus.PLACED )
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doBreak( 1, 'Filler cell placeds' )
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# Getting the layers.
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technology = DataBase.getDB().getTechnology()
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metal2 = technology.getLayer( "METAL2" )
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metal3 = technology.getLayer( "METAL3" )
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via12 = technology.getLayer( "VIA12" )
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via23 = technology.getLayer( "VIA23" )
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# Build wiring for a.
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# Create RoutingPads first.
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rp1 = RoutingPad.create( a
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, Occurrence( xr2_1.getPlug( xr2_x2.getNet("i0")) )
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, RoutingPad.BiggestArea )
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rp2 = RoutingPad.create( a
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, Occurrence( a2_1.getPlug( a2_x2.getNet("i0")) )
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, RoutingPad.BiggestArea )
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# Then regular wiring.
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contact1 = Contact.create( rp1, via12, toDbU( 0.0), toDbU(-15.0) )
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contact2 = Contact.create( rp2, via12, toDbU( 0.0), toDbU( 10.0) )
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turn = Contact.create( a , via23, toDbU(10.0), toDbU( 35.0) )
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Horizontal.create( contact2, turn , metal2, toDbU(35.0), toDbU(2.0) )
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Vertical .create( turn , contact1 , metal3, toDbU(10.0), toDbU(2.0) )
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UpdateSession.close()
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af.saveCell( fulladder, Catalog.State.Views )
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return
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def ScriptMain ( **kw ):
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editor = None
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if kw.has_key('editor') and kw['editor']:
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editor = kw['editor']
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buildFulladder( editor )
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return True
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