Cadence Mixed-Signal Circuit Design Environment User Guide
Obtaining an Initial Solution
October 2003
188
Product Version 5.0
Zero Delay
The advantage of the zero delay relaxation method is that it allows the reset solution of the
design to occur at time 0+, as shown in the following diagram.
A reset solution at time 0+ can make programming of the transient test stimuli easier because
you do not have to be concerned with the nonzero reset time.
There are some difficulties with the zero delay relaxation algorithm.
s
The logic simulator requires zero-delay models to do zero-delay logic simulation, but
zero-delay models might not be readily available.
s
The circuit simulator might be required to find several DC solutions in the iteration loop,
but DC solutions might be slow and difficult to find.
s
The iteration loop might not terminate unless
VMX_MAX_DC_ITER
is set to some small
value.
s
The digital circuitry might contain an X-state after the iteration loop terminates.
Transient test stimuli
t_0+
t_reset analog
t_final analog
Time
Stimuli
Application
Design
Solution
Reset stimuli
Final transient
solution
Digital
Analog
t_reset digital
t_final digital
Reset solution
Initial solution
Summary :
Cadence Mixed-Signal Circuit Design Environment User Guide Obtaining an Initial Solution October 2003 188 Product Version 5.0 Zero Delay The advantage of the zero delay relaxation method is that it allows the reset solution of the design to occur at time 0+, as shown in the following diagram.
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