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<TITLE>Magic-7.3 Command Reference</TITLE>
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<H1> <IMG SRC=graphics/magic_title2.gif ALT="Magic VLSI Layout Tool Version 7.3">
<IMG SRC=graphics/magic_OGL_sm.gif ALIGN="top" ALT="*"> </H1>
<H2>port</H2>
<HR>
Declare a label to be a subcircuit port, or manipulate port parameters.
<HR>
<H3>Usage:</H3>
<BLOCKQUOTE>
<B>port</B> <I>option</I> <BR><BR>
<BLOCKQUOTE>
where <I>option</I> may be one of the following:
<DL>
<DT> </I>index</I> <I>directions</I>
<DD> Declare a label to be a port with order number
<I>index</I> and with allowed connection directions
specified by the list <I>directions</I>. This is
equivalent to the <B>make</B> option, except that
the index and direction must be specified.
<DT><B>class</B> [<I>type</I>]
<DD> Get [set] port class type (see Summary, below).
<DT> <B>use</B> [<I>type</I>]
<DD> Get [set] port use type (see Summary, below).
<DT> <B>index</B> [<I>number</I>]
<DD> Get [set] port number
<DT> <B>equivalent</B> [<I>number</I>]
<DD> Make the port equivalent to the (other) port numbered
<I>number</I>.
<DT> <B>connections</B> [<I>directions</I>]
<DD> Get [set] port connection directions
<DT> <B>make</B> [</I>index</I>] [<I>directions</I>]
<DD> Declare a label to be a port with order number
<I>index</I> and with allowed connection directions
specified by the list <I>directions</I>. If not
specified, the index is set to the first unused
number, starting with 1, and the direction defaults
to the direction of the label text. That is, if the
label text is drawn to the right of the port, then
connections are allowed to the right side of the
port.
<DT> <B>remove</B>
<DD> Turn a port back into an ordinary label, removing
all of its port properties.
<DT> <B>help</B>
<DD> Print help information
</DL>
</BLOCKQUOTE>
</BLOCKQUOTE>
<H3>Summary:</H3>
<BLOCKQUOTE>
The <B>port</B> command turns labels into ports and
manipulates the properties of those ports. The <B>port</B>
command gives <B>magic</B> some understanding of "standard
cells". A cell definition that contains declared ports is
treated specially by the <B>extract</B>, <B>ext2spice</B>,
<B>lef</B>, and <B>def</B> commands. All other commands
interpret ports as ordinary labels. <B>ext2spice</B> only
interprets ports specially if the option <B>ext2spice subcircuits
on</B> is enabled. Cells that contain port labels are assumed
in these cases to be <I>standard cells</I>, that is, cells
which are pre-characterized, and for which the layout is not
to be interpreted as a physical circuit. When writing SPICE
output, a cell containing port labels that is a descendent cell
of the top-level layout is written as a subcircuit call, that
is, an "X" record. If the top-level cell in the layout
contains ports, then the SPICE output is written as a subcircuit
definition, that is, wrapped in a ".subckt . . . .ends" pair.
For LEF files, a cell that contains ports is written as a
macro cell, and the ports are the declared PINs of the macro.
For DEF files, a cell that contains ports is written as a
COMPONENT. <P>
The "index" property of the port is used only when the
cell is written into a SPICE deck as a subcircuit entry,
when the <B>ext2spice subcircuit on</B> option is enabled
(which it is by default). In that case, the subcircuit
call parameters (nodes) are written in the order of the port
indices, which are then assumed to match the definition for
the subcircuit. Likewise, if the circuit is written as a
subcircuit to a SPICE file, the order of parameters in the
subcircuit definition will match the order of the port
indices. Note that the actual port numbers are ignored;
the port values will be written in ascending order starting
with the lowest numbered port and ending with the highest
numbered port. <P>
The "direction" property of the port has no particular
meaning to magic but may be used by other programs to control
the allowed direction of routes into a standard cell. <P>
The "class" and "use" properties of the port have no
internal meaning to magic but are used by the LEF and DEF
format read and write routines, and match the LEF/DEF
CLASS and USE properties for macro cell pins. Valid
classes are: <B>default</B>, <B>input</B>, <B>output</B>,
<B>tristate</B>, <B>bidirectional</B>, <B>inout</B>,
<B>feedthrough</B>, and <B>feedthru</B>. Valid uses are:
<B>default</B>, <B>analog</B>, <B>signal</B>, <B>digital</B>,
<B>power</B>, <B>ground</B>, and <B>clock</B>.
</BLOCKQUOTE>
<H3>Implementation Notes:</H3>
<BLOCKQUOTE>
<B>port</B> is implemented as a built-in command in <B>magic</B>.
</BLOCKQUOTE>
<H3>See Also:</H3>
<BLOCKQUOTE>
<A HREF=label.html><B>label</B></A> <BR>
<A HREF=lef.html><B>lef</B></A> <BR>
</BLOCKQUOTE>
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<TD> <A HREF=commands.html>Return to command index</A>
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<P><I>Last updated:</I> October 16, 2004 at 2:10pm <P>
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