ps8_hspice_matl

ps8_hspice_matl - Courtesy of Michael Perrott. Used with...

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Unformatted text preview: Courtesy of Michael Perrott. Used with permission HSPICE Toolbox for MATLAB Michael Perrott http://www-mtl.mit.edu/perrott Copyright 1999 by Silicon Laboratories, Inc. 3 June 2003 Note: This software is distributed under the terms of the GNU Public License (see the included COPYING file for more details), and comes with no warranty or support. The Hspice toolbox for Matlab is a collection of Matlab routines that allow you to manipulate and view signals generated by Hspice simulations. The primary routine is a mex program called loadsig that reads binary output files generated by Hspice transient, DC, and AC sweeps into Matlab. The remaining routines are used to extract particular signals and view them. We will begin this document by explaining how to include the Hspice toolbox in your Matlab session. A list of each of the current functions will then be presented. Finally, we will provide examples of using these routines to view and postprocess signals from Hspice output files. Setup To use the Hspice toolbox, simply place the included files into a directory of your choice, and then add that directory to your Matlab path. For example, inclusion of the path '/home/user/matlab/bin' in Matlab can be done by adding the line addpath('/home/user/matlab/bin') to the file startup.m located in your home directory. In addition, you can specify the plot background to be black (similar to the look of Awaves) by adding another line to startup.m: colordef none; 1 Once you've made the above changes to startup.m, start Matlab as you normally would. Matlab will automatically read startup.m from your home directory and execute its commands. Platform Compatibility All files should work across different computer platforms, though the loadsig mexfile may need to be recompiled. It is currently compiled for Sun, Redhat Linux, and Windows 2000/Xp machines. To compile the loadsig function for a different platform, go to the directory containing loadsig.c within Matlab, and then type mex loadsig.c within Matlab. List of Functions The following functions are currently included in the Hspice toolbox: x = loadsig('hspice_output_filename'); Returns a Matlab structure into variable x that includes all of the signals that are present in the Hspice binary output file, hspice_output_filename. lssig(x) Lists all of the Hspice signal names present in the structure x. y = evalsig(x,'nodename'); Pulls out the signal nodename from the structure x and places into variable y. The string nodename can be an expression involving several Hspice signals. If you only performed one sweep in the simulation (as is common), then y will contain one column. If you performed several sweeps, y will contain several columns that correspond to the data for each sweep. If you have set the global Matlab variable sweep to a nonzero number, however, then y will contain only one column corresponding to the value of sweep. If sweep equals zero, all the sweep columns are included in y. plotsig(x,'plot_expression','optional_plotspec') Plots signals from the structure x according to the expression given in plot_expression. The string optional_plotspec is used to create logscale plots; it can be specified as logx, logy, or logxy. The string plot_expression specifies the nodenames, 2 and corresponding mathematical operations, that you would like to view. In this expression, commas delimit curves to be overlayed and semicolons delimit separate subplots on the same figure. All numeric node names should be prepended by '@' to distinguish them from constants. Some examples of using plotsig are: plotsig(x,'v1,v2;v3'): overlays v1 and v2 on the same subplot, and plots v3 on a separate subplot. plotsig(x,'(v1+v2)^2; log(abs(v3))'): plots the listed expressions on separate subplots. plotsig(x,'db(v1); ph(v1)','logx'): plots the magnitude (in dB) and phase (in degrees) of v1 on a semilogx axis. plotsig(x,'v1+@2+3'): plots the addition of node v1, node 2, and the constant 3. plotsig(x,'integ(TIME,v1); avg(TIME,v2)'): plots the integral of v1 and average of v2 on separate subplots. tzoom Brings up buttons on the plot to allow nice zooming functions. Type help tzoom at the Matlab prompt for more info. figname Allows easy labeling of figure windows. Type help figname at the Matlab prompt for more info. xlima Sets the x-limits of all subplots in a figure. Three options are possible: xlima: sets all subplots to the same x-axis as the last subplot that was zoomed into, xlima([xs xe]): sets all subplots to the x-axis limits specified, xlima('auto'): resets all subplots back to autoscaling. eyesig(x,period,start_off,'nodename') Creates an eye diagram for nodename contained in x with the specified period. All data samples prior to start_off are ignored when creating the diagram (useful for removing the influence of transient effects from the eye diagram). The string nodename can be an expression involving several variables. 3 Examples Viewing Signals Use the Matlab command cd to go to a directory containing a binary transient, DC, or AC sweep file generated from Hspice. We will assume a filename of test.tr0, and now list a series of Matlab commands that will be used to display nodes q and qb in that file. x = loadsig('test.tr0'); lssig(x) %% loads Hspice signals into x %% verify that nodes q and qb are present %% plot expressions of interest plotsig(x,'q; qb; q-qb') Doing Postprocessing in Matlab Use the Matlab command cd to go to a directory containing a binary transient, DC, or AC sweep file generated from Hspice. We will assume a filename of test.tr0, and now list a series of Matlab commands that will be used to postprocess nodes q and qb in that file. x = loadsig('test.tr0'); lssig(x) %% loads Hspice signals into x %% verify that nodes q and qb are present t = evalsig(x,'TIME'); %% loads time samples into Matlab variable t q = evalsig(x,'q'); %% loads signal q into Matlab variable q qb = evalsig(x,'qb'); %% loads signal qb into Matlab variable qb qdiff = q-qb; %% perform expressions in Matlab plot(t,q,t,qb,t,qdiff) %% plot variables using Matlab plot command 4 ...
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