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AR# 947

NC-Verilog - How do I back-annotate the SDF file for timing simulation?

Description

Keywords: NCV, Verilog, SDF, Cadence, timing, ncsim, nc-sim

Urgency: Standard

General Description:
How do I back-annotate the SDF file for timing simulation using NC-Verilog?

Solution

1

There are two methods for back-annotating delay values from an SDF file:

1. Compiling the SDF file at elaboration-time
2. Compiling the SDF file with NCSDFC

The NC-Verilog simulator only reads compiled SDF files; the SDF source file is supplied as an argument in a $sdf_annotate task by NetGen.

To compile the SDF file at elaboration-time:

Use the -autosdf option:

ncelab -autosdf <testfixture_name> glbl

The elaborator first determines if the $sdf_annotate argument is an SDF file or a compiled file. If it determines that it is an SDF file, it then looks for a corresponding compiled file ("sdf_filename.X"). If it doesn't find a corresponding compiled file, the elaborator issues a warning message and then spawns the NCSDFC utility to automatically compile the SDF file.

If a compiled file exists, NCSDFC checks to make sure that the date of the compiled file is newer than the date of the source file and that the version of the compiled file matches the version of NCSDFC. If either check fails, the SDF file is recompiled. Otherwise, the compiled file is simply read.

When invoked by the elaborator, the NCSDFC utility generates a log file called "sdf_filename.log".

2

To read the ASCII SDF file using the NCSDFC utility:

SDF files must be with NCSDFC to annotate the timing information contained in the SDF file:

ncsdfc sdf_filename.sdf

NCSDFC will create a file called "sdf_filename.sdf.X". If a compiled file exists, NCSDFC checks to make sure that the date of the compiled file is newer than the date of the source file and that the version of the compiled file matches the version of NCSDFC.

If either check fails, the SDF file is recompiled. Otherwise, the compiled file is simply read.
AR# 947
Date Created 08/21/2007
Last Updated 09/02/2004
Status Active
Type General Article