the solution of a system DAE in a continuous interval depends
solely on the unknowns at the beginning of interval
these values have to be solutions of the DAE
in general, there are several initial conditions that satisfy
the DAE, because during the initialization there are more unknowns that
equations ( x and dx/dt are the unknowns during the initialization)
an analog model built with VHDL-AMS distinguishes between
the effective initialization, that expands the initialization scheme
defined for VHDL and the operational initialization looking for
a quiescent point.
Quiescent point and
user specified initialization (break):
the quiescent point represents the DC operating
point of the model
the language defined the quiescent point of a model as the
state of the solution immediately before the postponed processes are about
to be executed at time 0.0.
in the absence of user specified initialization conditions,
the quiescent point is specified by:
dx/dt = 0
The initial conditions specified by the
user employ the same break instruction that is used to specify the
discontinuities:
break
qval1 => expression1, qval2 => expression2;
Initialization domains:
the simulator kernel controls the driver of the predefined
signal DOMAIN of enumerated type DOMAIN_TYPE
during the initialization, the value of the signal DOMAIN
is indexed to INITIALIZATION_DOM
when the quiescent point has been found the kernel
assigns a new value to the signal DOMAIN: TIME_DOMAIN if the quiescent
point has been found during a temporal simulation, and FREQUENCY_DOMAIN
if the simulation is frequential
consequently the postponed process is skipped to an
other delta cycle to update the signal DOMAIN
this means that it is possible reinitialize a process when
the quiescent point has been found, and to define the way used o find the
quiescent point, in temporal or in frequential simulation
