Release of an Upgraded SmartSpice
Interface to Cadence

 

The SmartSpice Interface to Cadence integrates the Analog Artist and Composer elements of the Cadence Design Framework II (DFII) with SmartSpice. This integration is accomplished, in versions 4.4.0 and later of DFII, through the Cadence Spice Socket (cdsSpice) and the OASIS interface in the Analog Artist and Composer components of DFII. Versions of DFII prior to 4.4.0 are also supported by SmartSpice, but these solutions rely on the older HSPICE Socket, and necessarily offer substantially less functionality than is provided by the current interface. This article will therefore concentrate on the OASIS/ Spice Socket version of the SmartSpice interface, first summarizing the development done to date, before going on to describe some significant enhancements which will be incorporated into the next release of the interface.

The SmartSpice interface is distributed as the Silvaco product "ssi_cds", with the version currently standing at 1.0.9.R. The interface can be installed into one or more existing platform-dependent installations of DFII with the command:

smartspice -oasis -install

The most obvious result of performing this installation will be seen when the Cadence Command Interpreter Window (CIW) is subsequently started up, as it will now contain (among other things) the line "Loading SmartSpice.cxt". The "Simulator" menu of Analog Artist's Simulator/Directory/Host control screen will now include "SmartSpice" among its available simulator modes; selecting this mode will enable the SmartSpice interface for that session of Artist. This means that Artist will now generate netlists in SmartSpice format, run SmartSpice transparently when required, and obtain the appropriate PSF output from SmartSpice necessary to enable all of the standard Artist/ Composer back-annotation and cross-probing functionality.

In order to take advantage of the SmartSpice-specific features now enabled, each user of Analog Artist will need to reference the Silvaco-supplied versions of the Cadence 'basic' and 'analogLib' component libraries. This is easily achieved by running the command:

smartspice -artist -configure

which will create a file called 'cds.lib.1.0.9.R' in the user's current working directory (assuming version 1.0.9.R of ssi_cds), the contents of which should be included in the user's 'cds.lib' file.

In the January 1998 edition of the Simulation Standard, the main capabilities of the current release of the SmartSpice interface were described in some detail; these will now be repeated here in summary:

  • Ability to specify SmartSpice as the default simulator in the Setup->Simulator/Directory/Host control screen of Analog Artist.
  • Ability to include model files in SmartSpice or cdsSpice format in the Setup->Environment control screen of Analog Artist.
  • Ability to generate PSF output from SmartSpice, implemented through automatic generation of the "psf=2" option.
  • Annotation of node voltages to the Composer schematic editor, selected via the Results->Annotate->DC Node Voltages menu item in Analog Artist.
  • Annotation of device operating points (for example, device currents, gds, etc.) to the Composer schematic editor, selected via the Results->Annotate->DC Operating Points menu item in Analog Artist, and controlled via the opPointLabelSet field of the Interpreted Labels Information section of the CDF properties in the Silvaco-supplied analogLib library, accessed via the Tools->CDF->Edit control screen in the Cadence CIW.
  • Support for marching waveforms, implemented via the SmartSpice waveform viewer through automatic generation of the ".IPLOT" statement.
  • Direct plot of waveforms in the Cadence Waveform Window, implemented via the Results->Direct Plot menu in Analog Artist, combined with user selection in the Composer schematic editor.
  • Hierarchical netlisting capability, implemented through SmartSpice/Spice Socket name mapping routines in the OASIS interface.
  • New Silvaco-supplied versions of the Cadence basic and analogLib libraries, incorporating SmartSpice views of all appropriate devices.
  • Compatibility with ac, dc, transient and noise analyses, via the Choosing Analyses control screen in Analog Artist.
  • Ability to save bias points in dc and transient analyses, via the Choosing Analysis control screen in Analog Artist.
  • Ability to configure the following SmartSpice options from within the Simulator Options control screen in Analog Artist:

ABSTOL, ACCT, ACCURATE, ACM, AUTOSTOP, BYPASS, CAPDC, CAPMOD, CAPTAB, CHGTOL, COEF1, CONV, DCGMCHK, DCGMIN, DCGMSTEPS, DCIAP, DCPATH, DEFAD, DEFAS, DEFL, DEFPD, DEFPS, DEFNRD, DEFNRS, DEFW, DISTRIBUTION, EXPERT, FORMAT, GMIN, GMINSTEPS, HDIF, ICG, INTEGR, INTERP, ITL1, ITL2, ITL4, ITL41, ITL5, LD, LDIF, LIMPTS, LIST, LOGIC, METHOD, NODE, NOMOD, NOPAGE, NUMDGT, OPTS, PIVREL, PIVTOL, RAWPTS, RELTOL, SCALE, SCALM, SRCSTEPS, TEMP, TNOM, TRTOL, TRYTOCOMPACT, TTICK, VNTOL, VSTA, VZERO, WIDTH

Since the release of version 1.0.9.R, some more substantial enhancements have been made to the SmartSpice interface. The most important, and immediately noticeable improvement has taken place in the Analog Artist user interface. In order to provide enhanced control over SmartSpice simulations, the analysis dialogs within Analog Artist have been redesigned to incorporate many more useful and requested SmartSpice features than are available in the current release.

The transient analysis dialog has been extended to support the following features:

  • Specification of either single time point syntax (via the "TSTEP", "TSTOP" and "TMAX" keywords) or multiple time point syntax.
  • Addition of several methods of operating point calculation, enabling the specification of initial conditions for circuits with multiple stable operating points (via the "UIC" option), the restoring and saving of operating points (the "CALLV"/"SAVEV" options) and support for simplifying the calculation of operating points for circuits with no path to ground (the "TRANOP" option).
  • Support for the "STORE" and "RAWPTS" options.

 

The AC and DC analysis dialogs have also received new attention:

  • Addition of the "UIC" and "CALLV"/"SAVEV" operating point options.
  • Addition of nested sweeps, providing the ability to sweep sources, component parameters, model parameters or temperature beneath the primary analysis, and allowing for selections to made directly on the schematic.

The new DC analysis dialog is illustrated in figure 1. Both new analyses take advantage of two useful features of the OASIS interface: all parameter values are automatically validated before being incorporated into input decks, and certain types of parameter (eg. sources, component parameters, etc.) can be selected directly from the schematic (see Figure 2).

 

Figure 1. The new dc analysis dialog box.

 

Figure 2. Source selection schematic.

 

 

Another important aspect of the forthcoming release of the SmartSpice interface is entirely hidden from the end user, but will result in a reduction in the development cycle for future releases. In the current version the input deck for SmartSpice is actually generated by the Cadence Spice Socket (cdsSpice), under control from Analog Artist. Any changes made to Analog Artist (through the OASIS interface) must also be reflected in cdsSpice. Therefore installation of a new version of the SmartSpice interface also requires a new version of cdsSpice. We are now able to take advantage of a recent enhancement to the OASIS interface allowing most of the input deck generation to be moved from cdsSpice to Analog Artist, thus minimizing the need for new versions of cdsSpice in the future.

This new version of the SmartSpice interface will be labeled 1.0.10.R, and will be available shortly.