Parallax Static Timing Analyzer

OpenSTA is a gate level static timing verifier. As a stand-alone executable it can be used to verify the timing of a design using standard file formats.

• Verilog netlist
• Liberty library
• SDC timing constraints
• SDF delay annotation
• SPEF parasitics

OpenSTA uses a TCL command interpreter to read the design, specify timing constraints and print timing reports.

Clocks

• Generated
• Latency
• Source latency (insertion delay)
• Uncertainty
• Propagated/Ideal
• Gated clock checks
• Multiple frequency clocks

Exception paths

• False path
• Multicycle path
• Min/Max path delay
• Exception points
• -from clock/pin/instance -through pin/net -to clock/pin/instance
• Edge specific exception points
• -rise_from/-fall_from, -rise_through/-fall_through, -rise_to/-fall_to

Delay calculation

• Integrated Dartu/Menezes/Pileggi RC effective capacitance algorithm
• External delay calculator API

Analysis

• Report timing checks -from, -through, -to, multiple paths to endpoint
• Report delay calculation
• Check timing setup

Timing Engine

OpenSTA is architected to be easily bolted on to other tools as a timing engine. By using a network adapter, OpenSTA can access the host netlist data structures without duplicating them.

• Query based incremental update of delays, arrival and required times
• Simulator to propagate constants from constraints and netlist tie high/low

See doc/OpenSTA.pdf for complete documentiaton.

Getting Started

OpenSTA can be run as a Docker container or built as local executable with CMake or Autotools.

Run using Docker

• Install Docker on Windows, Mac or Linux.
• Navigate to the directory where you have the input files.
• Run OpenSTA as a binary using

docker run -it -v $(pwd):/data openroad/opensta

4. From the interactive terminal, use OpenSTA commands. You can read input files from /data directory inside the docker container (e.g. read_liberty /data/liberty.lib). You can use OpenSTA in non-interactive mode by passing a command file using the -f flag as follows.

docker run -it -v $(pwd):/data openroad/opensta -f /data/cmd_file

Note that the path after -f is the path inside container, not on the guest machine.

Prerequisites

The build dependency versions are show below. Other versions may work, but these are the versions used for development.

         from   Ubuntu   Xcode
                18.04.1  10.1
cmake    3.9
clang    9.1.0           10.0.0
gcc      3.3.2   7.3.0   
tcl      8.2     8.6     8.6.6
swig     1.3.28  3.0.12  3.0.12
bison    1.35    3.0.4   2.3
flex     2.5.4   2.6.4   2.5.35

These packages are optional:

libz     1.1.4   1.2.5     1.2.8
cudd             2.4.1     3.0.0

CUDD is a binary decision diageram (BDD) package that is used to improve conditional timing arc handling. It is available here or here.

Note that the file hierarchy of the CUDD installation changed with version 3.0. Some changes to the CMake or configure scripts are required to support older versions.

You may use the --prefix option to configure to install in a location other than the default (/usr/local/lib).

cd $HOME/cudd-3.0.0
mkdir $HOME/cudd
./configure --prefix $HOME/cudd
make
make install

The Zlib library is an optional. If CMake or the configure script finds libz, OpenSTA can read Verilog, SDF, SPF, and SPEF files compressed with gzip.

Installing with CMake

Use the following commands to checkout the git repository and build the OpenSTA library and excutable.

git clone https://xp-dev.com/git/opensta
cd opensta
mkdir build
cd build
cmake .. -DCUDD=$HOME/cudd
make

The default build type is release to compile optimized code. The resulting executable is in app/sta. The library without a main() procedure is app/libSTA.a.

Optional CMake variables passed as -D= arguments to CMake are show below.

CMAKE_BUILD_TYPE DEBUG|RELEASE
CMAKE_CXX_FLAGS - additional compiler flags
TCL_LIB - path to tcl library
TCL_HEADER - path to tcl.h
CUDD - path to cudd installation ($HOME/cudd if following install shown above)
ZLIB_ROOT - path to zlib
CMAKE_INSTALL_PREFIX

If TCL_LIB is specified the CMake script will attempt to locate the header from the library path.

The default install directory is /usr/local. To install in a different directory with CMake use:

cmake .. -DCMAKE_INSTALL_PREFIX=<prefix_path>

Alternatively, you can use the DESTDIR variable with make.

make DESTDIR=<prefix_path> install

If you make changes to CMakeLists.txt you may need to clean out existing CMake cached variable values by deleting all of the files in the build directory.

Installing from a tarfile

Installing from a tarfile has the advantage that Autotools, bison, flex and swig do not need to be installed.

Use the following commands to unpack the dist file and compile it.

tar zvfz opensta-<version>.tgz
cd opensta-<version>
./configure [options...]
make

With no options, configure builds an optimized executable. The resulting executable is app/sta.

configure options:
  -h, --help              display configure help and exit
  --enable-debug          enable debug
  --enable-asan           enable AddressSanitizer
  --enable-gprof          enable gprof profiling
  --enable-gcov           enable gcov profiling
  --enable-32bit          force 32 bit compile
  --with-include=dirs     directories to search for include files
  --with-lib=dirs         directories to search for libraries
  --with-tcl=dirs         directories to search for Tcl init files
  --with-cudd=path        use Cudd BDD package, defaults to $CUDD
  --with-visualstudio     use Microcruft Visual Studio C++ compiler

If the configure script fails to find any of the TCL, Zlib or CUDD files, use the --with-include, --with-lib, --with-tcl, --with-cudd options to add directories to search for the files.

The configure --help option lists the generic configure options that are not described above. The default arguments to configure disable shared libraries. To build with shared libraries use the --enable-shared option.

Installing with Autotools

Building with GNU Autotools the additional build dependencies shown below.

         from   Ubuntu  Xcode
                18.04.1  10.1
autoconf 2.53    2.69    2.69
automake 1.6.3   1.15.1  1.16.1
libtool  1.4.2   2.4.6   2.4.6

Use the following commands to checkout the git repository and compile it.

git clone https://xp-dev.com/git/opensta
git checkout master|branch
./bootstrap
./configure [options...]
make

Configure options are show above in the "Installing from tarkit" section.

Installing on Windoz

The Win32 API does not natively support the pthreads API. The pthreads-win32 package is one way to get support for pthreads for 32 bit builds. It is available from pthreads. If the configure script does not find pthreads.h the build proceeds without thread support.

Use a .bat file to start a cygwin shell that has its path set to support the Microcruft cl compiler by calling the vsvars32.bat script from the Visual C++ installation.

tcsh-startup.bat
  @echo off
  call "c:\Microsoft Visual Studio 9.0\Common7\Tools\vsvars.bat"
  set path=c:\cygwin\bin;%PATH%
  c:\cygwin\bin\tcsh

CMake is supposedly more compatible with the windoz environment so you may have better luck wih it.

Configure and build from the shell. Note that tcl and zlib must be built with the Visual C++ compiler to link to the sta libraries. ... ./bootstrap ./configure --with-visualstudio make maintainer-clean ... Good luck and don't bother me with windoz specific issues. I am happy to say I haven't owned a windoz machine in 20 years.

Authors

• James Cherry

• William Scott authored the arnoldi delay calculator at Blaze, Inc which was subsequently licensed to Nefelus, Inc that has graciously contributed it to OpenSTA.

License

Copyright (c) 2019, Parallax Software, Inc. All rights reserved.

No part of this document may be copied, transmitted or disclosed in any form or fashion without the express written consent of Parallax Software, Inc.