Place and route tools do not require the full cell layout
Another view of the standard cells called the abstract view needs to generated
The abstract view provides information like:
n Cell name, site name, cell orientation
n Pin names, locations, pin metal layer, type and direction (input/output/input-output)
n Also provides location of all metal track and vias in the layout (obstructions)
This information is passed to the P & R tool in the LEF format (Library Exchange Format)
The LEF file contains technology information along with all the cell descriptions
We will use Cadence Abstract Generator tool for producing the abstract view from your standard cell layout view
Inverter (invx1) Abstract View
NAND (nand2x4) Abstract View
Technology File for Abstract
The abstract generator requires modifications to the technology file from NCSU that you use for your layouts
The new technology file with these modifications is available on my webpage
Warning: This library is read-only, do not change these permissions
Create a new library and attach the above library as the technology library to it
The input to the abstract generator is either the layout view or the GDS II description of the standard cells
To bring the cells from you design library into the new library above, dump the GDS II view of all you layouts from the design library and read them into the new library
Again modifications are required to the NCSU provided GDS II layer map file
Download the modified file from my webpage
On the CIW, click File -> Export -> Stream
The stream export form pops up
Fill in the required information
n Cell Name you want to dump
n Output GDS II file name (.gds)
Click on
User-Defined Data tab on the
Stream Out Form
In the Layer Map Table
field put the path to the layermap file you downloaded from my webpage (ami06_StreamLayerMap.txt)
Hit OK, the log is produced in a file called PIPO.log. Check the file to make sure you don't have any errors or warnings. The only warning it should have is that the technology library is unwrittable (we want this).
Now you can import the layout into your new library and generate the abstract view
Use CIW File -> Import -> Stream
Provide GDS II filename, cell name (same as before) and the library (new library)
Invoke the Abstract Generator using
abstract from the same directory where you run
icfb
Click File -> Library -> Open and select the new library that you created
Click File -> General Options. Under the general tab make sure the values are
CORE for
default bin and
5.5 for
LEF Version
Abstract Generation requires four steps
n Pins (extracts pin information using overlap of text and metal)
n Extract (connects all the shapes that fall on a single net)
n Abstract (combines information from above steps and generates blockages)
n Verify (verifies that the cell is properly constructed using a target P & R tool)
Before you can start the process you need to setup the options for each of these steps
The options are saved in a file called .abstract.options inside the directory for your library
My abstract options file is provided on the webpage. Copy this file into your library.
We will discuss each of the options with a live demo in the class