State-Space model is supported.

Calculate this equation with given A/B/C/D matrix using built in 4-degree rungekutta.
Calling Procedure ;.

$runge_kutta("File Name",mode,Input_RealArray,Output_RealArray,[X])；

• File contains text coefficient for A/B/C/D.
• mode must be 0 at initial statement others(always) should be 1
• Give input vector u with Input_RealArray.
• Output_RealArray will get y result.
• Internal State X can be defined in HDL source as an option.

See example source of "bessel.vtakprj".
It simulates digital FM-Demudulator as below.

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Analog PLL Simulation

Fig. below shows typical analog pll block diagram.

Loop Filter transfer function is calculated per following equations.

Since Veritak Linear Simulator needs State-Space model, we must change the equation to State Space model. .
Matlab or Scilab can do this by tf2ss.
Following is an example.

C2=14e-12 C1=100e-12 R1=4.7e3 R1C1=R1*C1; C1_C2=C1+C2; C1C2R1=C1*C2*R1; b=[R1C1 1]; a=[C1C2R1 C1_C2 0]; [A,B,C,D] = tf2ss(b,a) freqs(b,a) save 'F:\samples\loop_filter.txt' A B C D -ascii -double

This script generate "loop_filter.txt" in samples folder.

Load "pll_test.vtakprj"
It may be a good example to start mixed analog/digital simulation.

Tips:
 An example based on classic control theory is shown in http://www.sugawara-systems.com/opencores/pll/pll.htm

See also user contributed linear system simulator per following section, which has more generic approach with full source by C++.