--- /dev/null
+## Copyright (C) 2006,2007,2008 Carlo de Falco
+##
+## This file is part of:
+## OCS - A Circuit Simulator for Octave
+##
+## OCS is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program (see the file LICENSE); if not,
+## see <http://www.gnu.org/licenses/>.
+##
+## author: Carlo de Falco <cdf _AT_ users.sourceforge.net>
+
+## -*- texinfo -*-
+##
+## @deftypefn{Function File} @
+## {[@var{a},@var{b},@var{c}]=} Mvoltagesources(@var{string},@var{parameters},@
+## @var{parameternames},@var{extvar},@var{intvar},@var{t})
+##
+## SBN file implementing models for voltage sources.
+##
+## @var{string} is used to select among models. Parameters are listed
+## as inner items. Possible models are:
+##
+## @enumerate
+## @item @var{string} = "DC" (Static indipendent voltage source)
+## @itemize @minus
+## @item V -> Current source value
+## @end itemize
+## @item @var{string} = "sinwave" (Sinusoidal indipendent voltage
+## source)
+## @itemize @minus
+## @item shift -> mean value of sinusoidal input
+## @item Ampl -> amplitude of sinusoidal wave
+## @item f -> frequency of sinusoidal wave
+## @item delay -> delay of sinusoidal wave
+## @end itemize
+## @item @var{string} = "pwl" (Piecewise linear voltage source)
+## @itemize @minus
+## @item takes as parameter times and values. For example @code{0 1 4 6}
+## means at time instant 0 value 1, at time instant 4 value 6, etc.
+## @end itemize
+## @item @var{string} = "squarewave" (Square wave)
+## @itemize @minus
+## @item low -> low-state value
+## @item high -> high-state value
+## @item tlow -> duration of low-state
+## @item thigh -> duration of high-state
+## @item delay -> delay of square wave
+## @item start -> starting voltage value
+## @end itemize
+## @item @var{string} = "step" (Voltage step)
+## @itemize @minus
+## @item low -> low-state value
+## @item high -> high-state value
+## @item tstep -> time instant of step transition
+## @end itemize
+## @item @var{string} = "VCVS" (Voltage controlled voltage source)
+## @itemize @minus
+## @item K -> Control parameter
+## @end itemize
+## @end enumerate
+##
+## See the @cite{IFF file format specifications} for details about
+## the output structures.
+##
+## @seealso{prs_iff,asm_initialize_system,asm_build_system}
+## @end deftypefn
+
+function [a,b,c] = Mvoltagesources (string,parameters,parameternames,extvar,intvar,t)
+
+ if isempty(intvar)
+ intvar = 0;
+ endif
+
+ switch string
+ ##LCR part
+ case "DC"
+ for ii=1:length(parameternames)
+ eval([parameternames{ii} "=" num2str(parameters(ii)) ";"])
+ endfor
+
+ j = intvar(1);
+
+ a = zeros(3);
+ b = [0 0 1;0 0 -1;1 -1 0];
+ c = [0 0 -V];
+ break
+ ## NLC part
+ case "sinwave"
+ for ii=1:length(parameternames)
+ eval([parameternames{ii} "=" num2str(parameters(ii)) ";"])
+ endfor
+
+ DV = shift+Ampl * sin(2*pi*(t+delay)*f );
+ j = intvar(1);
+
+ a = zeros(3);
+ b = [0 0 1;0 0 -1;1 -1 0];
+ c = [0 0 -DV]' + b * [extvar;intvar];
+ break
+
+ case "pwl"
+
+ times = parameters(1:2:end-1);
+ values= parameters(2:2:end);
+
+ DV = interp1(times,values,t,"linear","extrap");
+ j = intvar(1);
+
+ a = zeros(3);
+ b = [0 0 1;0 0 -1;1 -1 0];
+ c = [0 0 -DV]' + b * [extvar;intvar];
+ break
+
+ case "squarewave"
+ for ii=1:length(parameternames)
+ eval([parameternames{ii} "=" num2str(parameters(ii)) ";"])
+ endfor
+ if t<delay
+ if exist("start")
+ DV=start;
+ else
+ DV=low;
+ endif
+ else
+ T = tlow+thigh;
+ t = mod(t-delay,T);
+ if t<tlow
+ DV = low;
+ else
+ DV = high;
+ endif
+ endif
+ j = intvar(1);
+
+ a = zeros(3);
+ b = [0 0 1;0 0 -1;1 -1 0];
+ c = [0 0 -DV]' + b * [extvar;intvar];
+ break
+
+ case "step"
+ for ii=1:length(parameternames)
+ eval([parameternames{ii} "=" num2str(parameters(ii)) ";"])
+ endfor
+
+ if t<tstep
+ DV=low;
+ else
+ DV = high;
+ endif
+
+ j = intvar(1);
+
+ a = zeros(3);
+ b = [0 0 1;0 0 -1;1 -1 0];
+ c = [0 0 -DV]' + b * [extvar;intvar];
+ break
+
+ case "VCVS"
+ K = 1;
+ for ii=1:length(parameternames)
+ eval([parameternames{ii} "=" num2str(parameters(ii)) ";"])
+ endfor
+
+ j = intvar(1);
+
+ a = zeros(5);
+ b = [0 0 0 0 1;0 0 0 0 -1;0 0 0 0 0;0 0 0 0 0;1 -1 -K K 0];
+ c = zeros(5,1);
+ break
+ otherwise
+ error (["unknown section:" string])
+ endswitch
+
+endfunction