AccuCell QA and Audit Options and Methods

012_cell : AccuCell QA and Audit Options and Methods

Minimum Required Versions: AccuCell 2.6.0.R, SmartSpice 4.6.2.R, SmartView 2.26.1.R

This example explains the use of AccuCell's quality assurance and audit options.

In addition to the above characterization and modeling options, AccuCell can also generate a basic datasheet and perform AVG power and MAX frequency characterizations although these play no roll in the Liberty and verilog model generation process. Also since AccuCell derives the function of each cell independently by analysis of the netlist structure and device types, cells of unknown behavior can be characterized and functionality automatically determined and documented in reverse-engineering situations which can prove to be an invalueable tool for checking and validating this type of work.

AccuCell also has a special "Audit" mode that can be enabled by setting USE_SMARTSPICE_API 0, SIM_DECK_LOG 1, VERBOSE 1 in the library level Cell_EX12.cfg file. This permits the inspection and review of all SPICE characterization input decks and output results in SmartSpice / SmartView with the -celltest mode.

NOTE: This mode is NOT intended to be used for normal characterization runs due to heavy disk I/O. Runtimes will be significantly increased. Therefore use of this mode is suggested for re-running cells and characterizations of interest once specific issues have been identified for a detailed review by preliminary examination of primary output results or random audit methods.

To run a specific version of AccuCell add the -V <version_name> switch like as follows:

accucell -V 2.6.0.R my.tcl

To run a specific version of SmartSpice add the .cfg command SMARTSPICE_VERSION <smartspice_version_name>.

ex. SMARTSPICE_VERSION 4.6.2.R

Audit files are written into a special sim_run directory in each cell sub-dir. Each individual simulation is a separate SPICE deck although multiple measurements that can be grouped together may exist in any given SPICE deck for simulation efficiency.

A quick visual review of most Liberty .lib results can be quickly achieved by the use of Smartview to inspect for relative timing surface smoothness and/or monotonicity.

Sample plots of the various NLDM and NLPM tables are included in various .png files. Full plot details can be reviewed after running the example and loading the resulting inv_sps.lib file into Smartview. Change the file type to "AccuCell (.lib)" to enable this. Then click on the desired arc table to plot it on the screen.

NOTE: At this time ONLY 2D tables can be graphed. To visualize other data fields please use a spreadsheet program or other method.

To aid in the review of monotonicity the .cfg file option CHECK_LUT 1 can be used to report warnings of non-monotonic values in a table as a function of the index parameters.

NOTE: ONLY warning reports are issued data is NOT corrected or smoothed by this command.

It is recommended that these warnings be reviewed to assure that no material problems exist. Monotonicity deviations should be minimal to be considered acceptable in most cases.

The .cfg file command GENERATE_TBL_FILE 1 can be used to control the generation of an internal .tbl table file format vector file to permit inspection of vector details for the various phases of the characterization process.

Lastly, when performing the initial characterization setup and debugging process the following .cfg commands can be used to bypass SPICE simulation and otherwise validate the proper .cfg settings: CONST_DELAY, DEFAULT_FF_SETUP, DEFAULT_FF_HOLD, DEFAULT_LATCH_SETUP, DEFAULT_LATCH_HOLD plus disabling any other CALC_, CHAR_ .cfg file commands (ex. CALC_C_EFF 0 ).