User Guide

Creating and Editing Hierarchical Symbols
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Creating and Editing Hierarchical
Symbols
PSpice Schematics uses two basic types of symbols:
primitive and hierarchical.
Primitive symbols are low level symbols that
explicitly contain all of the information required by the
netlister. They can be modified by editing their graphics,
pins, and attribute lists in the symbol editor.
Hierarchical symbols have the same appearance as
primitive symbols in PSpice Schematics. They contain one
or more levels of schematics inside them while primitive
symbols do not. They can also be modified by pushing
into them from within the schematic editor or symbol
editor and editing the associated schematics.
Creating a Hierarchical Symbol
The Symbolize function automatically creates a symbol to
represent a schematic. The symbol editor is then used to
modify any portion of the resulting symbol (graphics,
pins, and attributes).
When preparing a schematic for symbolization, follow
these guidelines:
• Place input and output interface ports (IF_IN,
IF_OUT) at the inputs and outputs of the schematic.
Interface ports are mapped to I/O pins placed on the
left (input) and right (output) of the new symbol.
• Place global ports (GLOBAL or BUBBLE) to bring out
global nets or connections as hidden pins. Global ports
are mapped to hidden pins placed on the top and
bottom of the new symbol. An
IPIN(xxx) attribute,
with a value that is the name of the net that it is
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Schematics symbol libraries are primitive.
Note that a symbol, for example, a
flip-flop, may be primitive for a PCB
netlister, but hierarchical for PSpice.
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levels of nesting allowed in a symbol.
Nesting of hierarchical symbols or blocks
w
ithin other hierarchical symbols or blocks
is possible.