User`s guide

Startin
g
Worst-Case Timin
g
Analysis 16
-3
Startin
g
Worst-Case
Timin
g
Anal
y
sis
1
In the Analysis Setup dialog box, click on the Digital Setup
button. Set Timing to Worst-Case (Min/Max, and complete
the rest of the Digital Setup dialog box as needed. Click on
OK when finished.
2
If needed, in the Analysis Setup dialog box, select (
✓) the
Digital Setup check box to enable it.
3
Start the simulation as described in Starting Simulation
on
page 8-11.
Simulator
Representation of
Timin
g
Ambi
g
uit
y
PSpice A/D relies on the use of the five-valued state
representation {0,1,R,F,X}, where R and F represent rising and
falling transitions, respectively. Any R or F transitions can be
thought of as ambiguity regions. Although the starting and final
states are known (example: R is a 0 → 1 transition), the exact
time of the transition is not known except to say that it occurs
somewhere within the ambiguity region. In other words, the
time interval between the earliest and the latest time that a
transition could occur is the ambiguity region.
Timing ambiguities propagate through digital devices via
whatever paths are sensitized to the specific transitions
involved. This is normal logic behavior. The delay values
(MIN, TYP, or MAX) skew the propagation of such signals by
whatever amount of propagation delay is associated with each
primitive instance.
When worst-case (MIN/MAX) timing operation is selected,
both the MIN and the MAX delay values are used to compute
See Setting Up Analyses on
page 8-3 for a description of the
Analysis Setup dialo
g
box.