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Template (Parameterized) Cells
Template cells, or parameterized cells, are cells which in addition to
possibly containing fixed geometry, contain a script which creates
geometry. When a template cell is instantiated, parameters are
supplied to the script, so that the geometry can vary between
instantiations. A single template cell can replace numerous small
cells representing contacts, vias, and devices. Use of template cells
can streamline the design process and reduce errors.
Template cells differ from ordinary cells in the following ways:
- The name of a template cell must be in the form
cellnameXXX
where the cellname is arbitrary, but must be followed by the
characters ``XXX'' (three upper-case `X' characters). The
``XXX'' is replaced internally by an identifying code which
is used to distinguish between instances with different parameter
sets.
- Template cells have a special property, the Template Script
property, which is assigned property number 7199. The string
of this property is a script that will be executed when the cell
is instantiated. The format of the script is conventional, and
any of the geometry creation and related functions can be used.
- Template cells may have an optional Template Params
property which is assigned number 7198. The string of this
property is a comma separated list of assignments, e.g.,
length=100,width=20,bottom=2,layer=R1
Each of the length, width, etc. are arbitrary
parameter names, that is, names of variables used in the script,
but not generally defined in the script. The values are taken as
default values for the parameters, and can be numeric values or
strings. If a value string contains white space, it must be
double quoted ("like this"). If the value token is a string
constant, i.e., the double quotes should be preserved, then the
value should be both single and double quoted ('"like
this"'). The value string can also be an executable code
fragment using only parameters already defined (to the left) and
constants, for example
param1=2,param2="param1 + 1"
Either the physical or electrical part of a symbol can be a template
cell, or both. A template cell can contain geometry, subcells, and
properties just like any other cell.
Subsections
Next: How Template Cells Work
Up: Using Xic
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Stephen R. Whiteley
2012-04-01