339 lines
12 KiB
ReStructuredText
339 lines
12 KiB
ReStructuredText
.. -*- Mode: rst -*-
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.. include:: ../etc/definitions.rst
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.. include:: ./definitions.rst
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3. Making a Standard Cell -- Layout
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===================================
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In this part, we will show how to create and save a terminal Cell_,
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that is, a cell without instances (the end point of a hierarchical
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design). To illustrate the case we will draw the layout of a
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standard cell.
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We will introduce the following classes : Cell_, Net_, Component_
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and its derived classes.
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3.1 The AllianceFramework (CRL Core)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The |Hurricane| database only manages objects in memory. To load or save
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something from the outside, we need to use a *framework*. As of today, only
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one is available : the Alliance framework. It allows |Coriolis| to handle
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|Alliance| libraries and cells in the exact same way.
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.. note:: To see how the AllianceFramework_ is configured for your
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installation, please have a look to ``alliance.conf`` in the
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``etc/coriolis2`` directory. It must contains the same settings
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as the various ``MBK_`` variables used for |Alliance|.
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3.2 Session Mechanism (Hurricane)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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In the |Hurricane| database, all modifications must take place inside
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an UpdateSession_. At the closing of a session, created or modificated
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objects are fully inserted in the database. This is especially true for
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the visualisation, a created component will be visible *only* only after
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the session close.
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.. note:: See ``QuadTree`` and ``Query``.
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3.3 Creating a new Cell (CRL Core)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The creation of a new Cell_ occurs through the AllianceFramework_,
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and, as stated above, inside a UpdateSession_. The AllianceFramework_
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environment is provided by the |CRL| module.
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.. code-block:: Python
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from Hurricane import *
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from CRL import *
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af = AllianceFramework.get()
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UpdateSession.open()
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cell = af.createCell( 'my_inv' )
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# Build then save the Cell.
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UpdateSession.close()
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This is the simplest call to ``createCell()``, and in that case, the newly
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created Cell_ will be saved in the *working library* (usually, the current
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directory). You may supply a second argument telling into which library
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you want the Cell_ to be created.
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In the |Hurricane| Cell_ object, there is no concept of *view*, it contains
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completly fused logical (netlist) and physical (layout) views.
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3.4 The DbU Measurement Unit
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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All coordinates in the |Hurricane| database are expressed in DbU_
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(for *Database Unit*) which are integer numbers of foundry grid.
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To be more precise, they are fixed points numbers expressed in
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hundredth of foundry grid (to allow transient non-integer
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computation).
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To work with symbolic layout, that is, using lambda based lengths,
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two conversion functions are provided:
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* ``unit = DbU.fromLambda( lbd )`` convert a lambda :cb:`lbd` into a ``DbU``.
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* ``lbd = DbU.toLambda( unit )`` convert a ``DbU`` into a lambda :cb:`lbd`.
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In the weakly typed |Python| world, :cb:`lbd` is *float* while :cb:`unit`
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is *integer*.
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3.5 Setting up the Abutment Box
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To setup the abutment box, we use a Box_ which defines a box from
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the coordinates of the lower left corner ``(x1,y1)`` and upper left
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corner ``(x2,y2)``.
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.. code-block:: Python
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b = Box( DbU.fromLambda( 0.0) # x1
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, DbU.fromLambda( 0.0) # y1
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, DbU.fromLambda(15.0) # x2
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, DbU.fromLambda(50.0) ) # y2
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cell.setAbutmentBox( b )
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Or more simply:
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.. code-block:: Python
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cell.setAbutmentBox( Box( DbU.fromLambda( 0.0)
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, DbU.fromLambda( 0.0)
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, DbU.fromLambda(15.0)
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, DbU.fromLambda(50.0) ) )
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3.6 Adding Nets and Components
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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In the |Hurricane| terminology, a **component** is any kind of physical object
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among:
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* Contact_
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* Pad_
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* RoutingPad_
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* Horizontal_
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* Vertical_
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* Plug_ is the only exception and will be detailed later (see ??).
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Components_ cannot be created *alone*. They must be part of a Net_.
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3.6.1 Getting a Layer
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---------------------
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As physical elements, Components_ are created using a Layer_. So prior to
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their creation, we must get one from the database. Layers_ are stored in the
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Technology_, which in turn, is stored in the DataBase_. So, to get a
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Layer_:
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.. code-block:: Python
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layer = DataBase.getDB().getTechnology().getLayer( 'METAL1' )
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.. note:: **Convention for layer names.** As the database can manage both real layers
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and symbolic ones we adopt the following convention:
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* **Real layers** are named in lowercase (``metal1``, ``nwell``).
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* **Symbolic layers** are named in uppercase (``METAL1``, ``NWELL``).
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3.6.2 Creating a Net
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--------------------
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As said above, prior to creating any Component_, we must create the Net_ it
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will belong to. In that example we also make it an *external* net, that is,
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a part of the interface. Do not mistake the name of the net given as a string
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argument :cb:`'i'` and the name of the *variable* :cb:`i` holding the Net_ object.
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For the sake of clarity we try to give the variable a close name, but this is
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not mandatory.
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.. code-block:: Python
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i = Net.create( cell, 'i' )
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i.setExternal( True )
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.. note:: Unlike some other database models, in |Hurricane|,
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**there is no explicit terminal object**, you only need to make the
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net external. For more information about how to connect to an
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external net, see `6.2 Creating Nets and connecting to Instances`_.
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3.6.3 Creating a Component
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--------------------------
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Finally, we get ready to create a Component_, we will make a Vertical_ segment
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of ``METAL1``.
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.. code-block:: Python
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segment = Vertical.create( i # The owner Net.
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, layer # The layer.
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, DbU.fromLambda( 5.0 ) # The X coordinate.
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, DbU.fromLambda( 2.0 ) # The width.
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, DbU.fromLambda( 10.0 ) # The Y source coordinate.
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, DbU.fromLambda( 40.0 ) ) # The Y target coordinate.
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With this overload of the ``Vertical.create()`` function the segment is created at an
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absolute position. There is a second overload for creating a relatively placed
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segment, see *articulated layout*.
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If the net is external, that is, part of the interface of the cell, you may have
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to declare some of its components as physical connectors usable by the router.
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This is done by calling the NetExternalComponents_ class:
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.. code-block:: Python
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NetExternalComponents.setExternal( segment )
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3.7 Saving to Disk (CRL Core)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Once you have finished to build your cell, you have to save it on disk.
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Using the AllianceFramework_ you can save it as a pair of file:
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========================= =================================== =======================
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View Flag File extension
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========================= =================================== =======================
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Logical / Netlist ``Catalog.State.Logical`` ``.vst``
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Physical / Layout ``Catalog.State.Physical`` ``.ap``
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========================= =================================== =======================
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To save both views, use the ``Catalog.State.Views`` flag. The files
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will be written in the |Alliance| ``WORK_DIR``.
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.. code-block:: Python
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af.saveCell( cell, Catalog.State.Views )
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3.8 The Complete Example File
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The example files 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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The code needed to run it through the |cgt| viewer has been added. For the
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explanation of that part of the code, refer to `5. Make a script runnable through cgt`_.
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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 buildInvertor ( editor ):
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UpdateSession.open()
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cell = AllianceFramework.get().createCell( 'invertor' )
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cell.setTerminal( True )
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cell.setAbutmentBox( Box( toDbU(0.0), toDbU(0.0), toDbU(15.0), toDbU(50.0) ) )
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if editor:
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UpdateSession.close()
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editor.setCell( cell )
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editor.fit()
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UpdateSession.open()
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technology = DataBase.getDB().getTechnology()
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metal1 = technology.getLayer( "METAL1" )
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poly = technology.getLayer( "POLY" )
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ptrans = technology.getLayer( "PTRANS" )
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ntrans = technology.getLayer( "NTRANS" )
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pdif = technology.getLayer( "PDIF" )
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ndif = technology.getLayer( "NDIF" )
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contdifn = technology.getLayer( "CONT_DIF_N" )
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contdifp = technology.getLayer( "CONT_DIF_P" )
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nwell = technology.getLayer( "NWELL" )
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contpoly = technology.getLayer( "CONT_POLY" )
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ntie = technology.getLayer( "NTIE" )
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net = Net.create( cell, "nwell" )
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Vertical.create( net, nwell, toDbU(7.5), toDbU(15.0), toDbU(27.0), toDbU(51.0) )
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vdd = Net.create( cell, "vdd" )
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vdd.setExternal( True )
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vdd.setGlobal ( True )
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h = Horizontal.create(vdd, metal1, toDbU(47.0), toDbU(6.0), toDbU(0.0), toDbU(15.0) )
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NetExternalComponents.setExternal( h )
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Contact.create ( vdd, contdifn, toDbU(10.0), toDbU(47.0), toDbU( 1.0), toDbU( 1.0) )
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Contact.create ( vdd, contdifp, toDbU( 4.0), toDbU(45.0), toDbU( 1.0), toDbU( 1.0) )
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Vertical.create( vdd, pdif , toDbU( 3.5), toDbU( 4.0), toDbU(28.0), toDbU(46.0) )
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Vertical.create( vdd, ntie , toDbU(10.0), toDbU( 3.0), toDbU(43.0), toDbU(48.0) )
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doBreak( 1, 'Done building vdd.' )
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vss = Net.create( cell, "vss" )
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vss.setExternal( True )
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vss.setGlobal ( True )
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h = Horizontal.create(vss, metal1, toDbU(3.0), toDbU(6.0), toDbU(0.0), toDbU(15.0))
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NetExternalComponents.setExternal( h )
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Vertical.create( vss, ndif , toDbU(3.5), toDbU(4.0), toDbU(4.0), toDbU(12.0) )
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Contact.create ( vss, contdifn, toDbU(4.0), toDbU(5.0), toDbU(1.0), toDbU( 1.0) )
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doBreak( 1, 'Done building vss.' )
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i = Net.create( cell, "i" )
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i.setExternal( True )
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v = Vertical.create ( i, metal1, toDbU(5.0), toDbU(2.0), toDbU(10.0), toDbU(40.0) )
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NetExternalComponents.setExternal( v )
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Vertical.create ( i, ptrans , toDbU( 7.0), toDbU( 1.0), toDbU(26.0), toDbU(39.0) )
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Vertical.create ( i, ntrans , toDbU( 7.0), toDbU( 1.0), toDbU( 6.0), toDbU(14.0) )
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Vertical.create ( i, poly , toDbU( 7.0), toDbU( 1.0), toDbU(14.0), toDbU(26.0) )
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Horizontal.create( i, poly , toDbU(20.0), toDbU( 3.0), toDbU( 4.0), toDbU( 7.0) )
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Contact.create ( i, contpoly, toDbU( 5.0), toDbU(20.0), toDbU( 1.0), toDbU( 1.0) )
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doBreak( 1, 'Done building i.' )
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nq = Net.create ( cell, "nq" )
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nq.setExternal( True )
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v = Vertical.create( nq, metal1, toDbU(10.0), toDbU(2.0), toDbU(10.0), toDbU(40.0) )
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NetExternalComponents.setExternal( v )
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Vertical.create( nq, pdif , toDbU(10.0), toDbU( 3.0), toDbU(28.0), toDbU(37.0) )
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Vertical.create( nq, ndif , toDbU(10.0), toDbU( 3.0), toDbU( 8.0), toDbU(12.0) )
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Contact.create ( nq, contdifp, toDbU(10.0), toDbU(35.0), toDbU( 1.0), toDbU( 1.0) )
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Contact.create ( nq, contdifp, toDbU(10.0), toDbU(30.5), toDbU( 1.0), toDbU( 1.0) )
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Contact.create ( nq, contdifn, toDbU(10.0), toDbU(10.0), toDbU( 1.0), toDbU( 1.0) )
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doBreak( 1, 'Done building q.' )
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UpdateSession.close()
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AllianceFramework.get().saveCell( cell, 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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buildInvertor( editor )
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return True
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