psf-utils 1.10
Cadence PSF file utilities
Requires Python: >=3.6
Keywords: cadence, spectre, PSF, simulation

PSF Utilities — Read Spectre Data Files
=======================================

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:Author: Ken Kundert
:Version: 1.10
:Released: 2025-07-30


What?
-----

*psf_utils* is a library that allows you to read data from a Spectre PSF ASCII 
file.  Spectre is a commercial circuit simulator produced by Cadence Design 
Systems.  PSF files contain signals generated by Spectre.  This package also 
contains two programs that are useful in their own right, but also act as 
demonstrators as to how to use the library. They are *list-psf* and *show-psf*.  
The first lists the available signals in a file, and the other displays them.


Accessing the Results
---------------------

You can use the PSF class to read ASCII Parameter Storage Format files. When
instantiating the class you pass in the path to the file and then the resulting
PSF object contains the signals. For example, the following lists the signals 
present in a ASCII PSF file::

    from psf_utils import PSF
    from inform import Error, display

    kinds = {
        'float double': 'real',
        'float complex': 'complex',
    }

    try:
        psf = PSF('adc.raw/tran.tran')

        for signal in psf.all_signals():
            kind = signal.type.kind
            kind = kinds.get(kind, kind)
            display(f'{signal.name:<15}  {signal.units:<12}  {kind}')
    except Error as e:
        e.terminate()

This example plots the output signal::

    from psf_utils import PSF
    from inform import Error, display
    import matplotlib.pyplot as plt

    try:
        psf = PSF('adc.raw/tran.tran')
        sweep = psf.get_sweep()
        out = psf.get_signal('out')

        figure = plt.figure()
        axes = figure.add_subplot(1,1,1)
        axes.plot(sweep.abscissa, out.ordinate, linewidth=2, label=out.name)
        axes.set_title('ADC Output')
        axes.set_xlabel(f'{sweep.name} ({PSF.units_to_unicode(sweep.units)})')
        axes.set_ylabel(f'{out.name} ({PSF.units_to_unicode(out.units)})')
        plt.show()
    except Error as e:
        e.terminate()

*abscissa* and *ordinate* are NumPy arrays.  As such, you can perform 
computation with them::

    out = out_p.ordinate - out_n.ordinate

    from numpy import sin
    sine = sin(sweep.abscissa)

Reading large ASCII data files is slow, so *psf_utils* reads the PSF file once,
then pickles the data and writes it to disk. On subsequent runs the pickled data
is used if the pickle file is newer that the corresponding PSF file.

Things are a bit different for DC operating point results. In this case, *sweep* 
is None and the results are scalar `quantities 
<https://quantiphy.readthedocs.io>`_::

    from psf_utils import PSF, Quantity

    psf = PSF('opamp.raw/op.dc')
    with Quantity.prefs(map_sf=Quantity.map_sf_to_greek):
        for signal in sorted(psf.all_signals(), key=lambda s: s.name):
            name = f'{signal.access}({signal.name})'
            print(f'{name:>20} = {signal.ordinate}')


Utility Programs
----------------

Two utility programs are installed along with the *psf_utils* library:
*list-psf* and *show-psf*. The first lists the signals available from a PSF
file, and the second displays them. They both employ caching to speed up access
to the data. They also cache the name of the PSF file so that it need not be
given every time. *show-psf* also caches its arguments, so if you run it again
with no arguments it will simply repeat what it did last time. For example, here
is a typical session::

    # list the signals in noise PSF file
    > list-psf -f resistor.raw/pnoise.pnoise
    Using resistor.raw/pnoise.pnoise.
        R1:flicker  R1:total    R2:fn       out
        R1:thermal  R2:rn       R2:total

    # list them again, this time in long form
    > list-psf -l
    Using resistor.raw/pnoise.pnoise.
        R1:flicker  A²/Hz  real  (12042 points)
        R1:thermal  A²/Hz  real  (12042 points)
        R1:total    A²/Hz  real  (12042 points)
        R2:fn       A²/Hz  real  (12042 points)
        R2:rn       A²/Hz  real  (12042 points)
        R2:total    A²/Hz  real  (12042 points)
        out         A/√Hz  real  (12042 points)

    # list only those that match R1:* (assumes nonomatch variable is set in shell)
    > list-psf -l R1:*
    Using resistor.raw/pnoise.pnoise.
        R1:flicker  A²/Hz  real  (12042 points)
        R1:thermal  A²/Hz  real  (12042 points)
        R1:total    A²/Hz  real  (12042 points)

    # show a graph containing signals that start with R1:
    > show-psf R1:*

    # show the thermal noise of R1, and then the total noise minus the flicker noise
    > show-psf R1:thermal R1:total-R1:flicker

    > show-psf out        # show a graph containing only out

    > show-psf            # show out again, exactly as in previous run

    > show-psf -M out     # show out again, this time include point markers

    > show-psf -P out     # show out again, this time only show point markers

    > show-psf -s out.svg out     # send graph of out to svg file

    # list signals in a PSF file from a DC operating point file:
    > list-psf -f diffamp.raw/tran.dc
    Using diffamp.raw/pnoise.pnoise.
        in_n    in_p    out_n   out_p   Vdd     Vdd:p

    # show the DC voltages
    > show-psf \*
         V(in_n) = 47.678 µV
         V(in_p) = 47.623 µV
        V(out_n) = 876.16 µV
        V(out_p) = 876.16 µV
          V(Vdd) = 2.5 V
        I(Vdd:p) = −10.05 µA

    # list signals in transient PSF file
    > list-psf -f diffamp.raw/tran.tran
    Using diffamp.raw/pnoise.pnoise.
        in_n    in_p    out_n   out_p   Vdd     Vdd:p

    # display differential output and differential input
    > show-psf out_p-out_n in_p-in_n


Converting to PSF ASCII
-----------------------

*psf_utils* only supports PSF ASCII files. As an alternative, `libpsf
<https://pypi.org/project/libpsf>`_ is a Python package that can read both ASCII
and binary PSF files. Or, you can use the Cadence *psf* program to convert
various types of simulation results files into PSF ASCII format. To use it,
simply specify the input and output files::

    > psf -i adc.raw/tran.tran -o adc.raw/tran.psfascii
    > list-psf -f adc.raw/tran.psfascii

In this example there is nothing special about the 'psfascii' suffix, it is
simply mnemonic.  Rather, the output is in ASCII format because the ``-b``
(binary) option is not specified.

*psf_utils* does not support SST files, which are generated by AMS Designer, 
Cadence's mixed-signal simulator. You can recognize SST files in that they come 
in pairs, and the two files have ``.dsn`` and ``.trn`` suffixes.  In this case, 
Cadence's PSF utility cannot help you either.  However, you can use the 
*simvisdbutil* to convert the data to a CSV file, which would allow you to 
access the data, though not with *psf_utils*.  For example, the following
converts all waveforms contained in ldo.trn into CSV data::

    simvisdbutil ldo.trn -csv -timeunits s -output ldo.csv


Examples
--------

`Flicker Noise <https://github.com/KenKundert/flicker-noise>`_ is a simulation 
script that shows how to write simple Python scripts that run Spectre and use 
*psf_utils* to extract and display the desired results.


Releases
--------

Latest development release
''''''''''''''''''''''''''

| Version: 1.10
| Released: 2025-07-30


1.10 (2025-07-30)
'''''''''''''''''
- Properly recognize real numbers with exponents but without decimal points.


1.9 (2025-04-08)
''''''''''''''''

- Added ``--major-grid`` and ``--minor-grid`` options to show command
- Fixed units on unitless numbers
- Other minor bug fixes


1.8 (2024-01-15)
''''''''''''''''

- Fixed issue with *NaN*


1.7 (2023-12-13)
''''''''''''''''

- fixed units on terminal currents
- add support for *inf*
- add support for *PZ* and *STB* files


1.6 (2022-09-18)
''''''''''''''''

- changed ``--no-cache`` command line option to ``--refresh-cache``.


1.5 (2021-11-11)
''''''''''''''''

- Renamed *plot-psf* to *show-psf*.
- Improved support of DC operating points.
- Suppress access function names when printing members of PSF structures.
- Correct invalid units produced by Spectre on oppoint files (I, R, C).


1.4 (2021-10-21)
''''''''''''''''

- Allow signal names to contain backslashes.


1.3 (2021-03-21)

- Improve support for DC operating points.


1.2 (2021-01-07)
''''''''''''''''

- Support PSF files that contain DC operating points.
- Support PSF files where values are given in a group.


1.1 (2021-01-30)
''''''''''''''''

- Allow, but ignore, properties on traces.


1.0 (2020-11-03)
''''''''''''''''

- Production release


.. hide the pre-production releases

    **0.7 (2020-09-23)**:
        - Add ability to show individual points
        - Improve the cursor values display
        - Increase precision of both cursor values and axis labels

    **0.6 (2020-04-16)**:
        - modest refinements

    **0.5 (2020-01-08)**:
        - beta release

    **0.4 (2019-09-26)**:
        - Allow glob patterns to be passed to both *list-psf* and *show-psf*.

    **0.3 (2019-09-25)**:
        - Fix import errors in *show-psf* command.

    **0.2 (2019-09-25)**:
        - Fix dependencies.

    **0.1 (2019-09-25)**:
        - Initial version