...set model characteristics
The software model of the CNN cells may be adapted in many ways.
Most of the parameters are set in the model section
of the simulator menu:
The user can choose between the following integration methods:
Euler: not very accurate, small integration steps, default integration
Modified Euler: more accurate than Euler.
Runge Kutta (4. order): often used, accurate.
The CNN simulator provides some useful nonlinear functions for the
software model of the CNN cells:
PWL (the standard piece wise linear function):
y= sat(x)= 1/2*(|p*x+1| - |p*x-1|)
Smooth PWL (a 'smooth' variant of the PWL function):
y= 1/(2*p)* ln(cosh(p*(x+1)) / cosh(p*(x-1)))
the breakpoint facility: The simulation will be suspended at the
breakpoint. It is possible to continue the simulation step by step after
suspend integration when network equilibrium is reached: The simulation
is suspended when the simulator detects network equilibrium. It is possible
to continue the simulation step by step after network equilibrium is reached.
For information about the algorithms to detect network equilibrium:
Short description of the CNN Simulator
the state limiter: In VLSI implementations of CNN, the state
voltage is limited to a certain value. To make the simulation more realistic,
the user can limit the state values of the software CNN cells to a certain
value. For more information about the basic circuit of a CNN cell see Architecture
of Cellular Neural Networks.
To set the model parameters, follow these steps:
Change to the model section using the simulator menu :
An integration method can be selected by using the choice widget.
The user controls integration step width using the three fields
The field on the left side controls the integration step width for
integration methods with constant integration step width.
The fields in the middle and on the right side control minimal and
maximal integration step width when integration methods with variable integration
step width are used.
An output function can be selected using the choice widget. It provides
an additional parameter p. Its effect is shown on the output pictures
Toggle the breakpoint option to enable or disable it. When enabled
you can enter the breakpoint time.
Toggle the equilibrium option to enable or disable it.
Toggle the state limiter to enable or disable it. When enabled you
can enter the limit for the cell state.
Finally press the "apply" button to accept the new settings.
The "reset" button resets the model section to the default values
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