Automatic Configuration From a Liberty File

002_cell : Automatic Configuration From a Liberty File

Requires: AccuCell & SmartSpice

Minimum Required Versions: AccuCell 2.6.0.R, SmartSpice 4.6.2.R

This example explains how to use the gen_cfg feature in AccuCell to automatically configure a simple inverter cell for characterization by referencing an existing Liberty .lib format timing model file. A related SILVACO Application Note 4-011 "Automatic Generation of Configuration Files for AccuCell" is also available on the SILVACO web site. This example compliments that application note.

To run gen_cfg You will need a Liberty .lib format timing file library_sps.lib and a special AccuCell configuration file specifically for the gen_cfg process gen_cfg.cfg.

gen_cfg is an AccuCell .Tcl command that can either be run interactively in the AccuCell Tcl shell which can be entered by typing

accucell

or can be entered into a .tcl script file gen_cfg.tcl. In either case the format of the command is as follows:

gen_cfg <gen_cfg_config_file>

The file <gen_cfg_config_file> is used to define the global POWERS and GROUNDS for the cell library. It also defines either a single file containing ALL cell netlist .SUBCKTs OR a directory containing separate files for each cell in the library. The parameter IN_FILE_NAME defines an absolute path directory for a single file containing ALL cell netlist .SUBCKTs. If IN_FILE_NAME_REL defines reletive path directory for any number of files can be specified. If IN_FILE_NAME_ABS defines absolute path to a single SPICE file containing all cell SUBCKTs. And a common file extension can be defined with the SUBCKT_EXTN command. The group of netlist file names must be in the form of the <cell_name> . <ext> where <ext> is the extension defined with the SUBCKT_EXTN command. Also use IN_SNPS_LIB_NAME defines the Synopsys liberty format library file. Additionally, if the slopes in the Liberty .lib timing file are to be ignored then the command SLOPE 0 can be included in the <gen_cfg_config_file> .

When a significate number of cells to be characterized exists, the use of gen_cfg can provide a significant reduction in the time to setup the library in AccuCell. All cell and pin attributes will be translated into cell level AccuCell .cfg file syntax commands and all library level attributes will also be translated into library level AccuCell .cfg syntax commands.