347 lines
12 KiB
ReStructuredText
347 lines
12 KiB
ReStructuredText
.. -*- Mode: 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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from helpers.overlay import UpdateSession
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af = AllianceFramework.get()
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with UpdateSession():
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cell = af.createCell( 'my_inv' )
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# Build then save the Cell.
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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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In order to reduce the number of characters one has to code, the :cb:`helpers`
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module provides three very short function to perform conversion *towards*
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DbU_ :
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.. code-block:: Python
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def l ( value ):
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"""Convert a lambda into a DbU."""
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return DbU.fromLambda( value )
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def u ( value ):
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"""Convert a length in micrometer into a DbU."""
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return DbU.fromPhysical( value, Hurricane.DbU.UnitPowerMicro )
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def n ( value ):
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"""Convert a length in nanometer into a DbU."""
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return DbU.fromPhysical( value, Hurricane.DbU.UnitPowerNano )
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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( l( 0.0) # x1
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, l( 0.0) # y1
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, l(15.0) # x2
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, l(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( l( 0.0), l( 0.0), l(15.0), l(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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, l( 5.0 ) # The X coordinate.
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, l( 2.0 ) # The width.
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, l( 10.0 ) # The Y source coordinate.
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, l( 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 DataBase, NetExternalComponents, Net, \
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DbU, Point, Box, Horizontal, Vertical, Contact, RoutingPad, \
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Breakpoint
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from CRL import AllianceFramework, Catalog
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from helpers import l
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from helpers.overlay import UpdateSession
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def doBreak ( level, message ):
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"""Put a breakpoint into the script."""
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Breakpoint.stop( level, message )
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def buildInvertor ( editor ):
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"""Build step by step an invertor standard cell."""
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with UpdateSession():
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cell = AllianceFramework.get().createCell( 'invertor' )
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cell.setTerminalNetlist( True )
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cell.setAbutmentBox( Box( l(0.0), l(0.0), l(15.0), l(50.0) ) )
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if editor:
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editor.setCell( cell )
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editor.fit()
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with UpdateSession():
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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, l(7.5), l(15.0), l(27.0), l(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, l(47.0), l(6.0), l(0.0), l(15.0) )
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NetExternalComponents.setExternal( h )
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Contact.create ( vdd, contdifn, l(10.0), l(47.0), l( 1.0), l( 1.0) )
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Contact.create ( vdd, contdifp, l( 4.0), l(45.0), l( 1.0), l( 1.0) )
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Vertical.create( vdd, pdif , l( 3.5), l( 4.0), l(28.0), l(46.0) )
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Vertical.create( vdd, ntie , l(10.0), l( 3.0), l(43.0), l(48.0) )
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doBreak( 1, 'Done building vdd.' )
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with UpdateSession():
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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, l(3.0), l(6.0), l(0.0), l(15.0))
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NetExternalComponents.setExternal( h )
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Vertical.create( vss, ndif , l(3.5), l(4.0), l(4.0), l(12.0) )
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Contact.create ( vss, contdifn, l(4.0), l(5.0), l(1.0), l( 1.0) )
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doBreak( 1, 'Done building vss.' )
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with UpdateSession():
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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, l(5.0), l(2.0), l(10.0), l(40.0) )
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NetExternalComponents.setExternal( v )
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Vertical.create ( i, ptrans , l( 7.0), l( 1.0), l(26.0), l(39.0) )
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Vertical.create ( i, ntrans , l( 7.0), l( 1.0), l( 6.0), l(14.0) )
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Vertical.create ( i, poly , l( 7.0), l( 1.0), l(14.0), l(26.0) )
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Horizontal.create( i, poly , l(20.0), l( 3.0), l( 4.0), l( 7.0) )
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Contact.create ( i, contpoly, l( 5.0), l(20.0), l( 1.0), l( 1.0) )
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doBreak( 1, 'Done building i.' )
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with UpdateSession():
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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, l(10.0), l(2.0), l(10.0), l(40.0) )
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NetExternalComponents.setExternal( v )
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Vertical.create( nq, pdif , l(10.0), l( 3.0), l(28.0), l(37.0) )
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Vertical.create( nq, ndif , l(10.0), l( 3.0), l( 8.0), l(12.0) )
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Contact.create ( nq, contdifp, l(10.0), l(35.0), l( 1.0), l( 1.0) )
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Contact.create ( nq, contdifp, l(10.0), l(30.5), l( 1.0), l( 1.0) )
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Contact.create ( nq, contdifn, l(10.0), l(10.0), l( 1.0), l( 1.0) )
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doBreak( 1, 'Done building q.' )
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AllianceFramework.get().saveCell( cell, Catalog.State.Views )
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def scriptMain ( **kw ):
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"""The Mandatory function to be run by Coriolis interactively."""
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editor = None
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if 'editor' in kw 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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