User Guide

Passing Information Between Levels of Hierarchy
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found at that level, PSpice Schematics then searches
the parent level. It continues up the hierarchy until it
either finds a definition or until it reaches the top of
the hierarchy.
• When PSpice Schematics finds an attribute, it
evaluates the attribute at the level where it is found. If
the attribute value refers to other attributes, those
other attributes must exist at the present level or
higher in the hierarchy.
For example, hierarchical symbol
A defines two attributes:
X=@Y and Y=10. Symbol A contains an instance of a symbol
B; B contains an expression referring to the attribute X
({@X}) and defines the value of attribute
Y to be 20
(Y=20)
.
The evaluation of the expression {
@X} is:
• X is searched for on the present level.
• There is no X attribute at this level, so the parent
environment (symbol
A) is searched.
• An attribute named X is found at this level—this
attribute is evaluated in the environment supplied
by
A.
• The first stage of this evaluation delivers the result
@Y—this is then processed to yield the result 10.
• The final result is to make the result of the
expression in
B be {10} ({@X}={10}).
• The definition for Y in the environment supplied
by symbol
B is not used when evaluating X in A’s
environment.