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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>lef</H2>
<HR>
LEF-format input and output
<HR>
<H3>Usage:</H3>
<BLOCKQUOTE>
<B>lef</B> <I>option</I> <BR><BR>
<BLOCKQUOTE>
where <I>option</I> may be one of the following:
<DL>
<DT> <B>read</B> [<I>filename</I>]
<DD> Read a LEF file named <I>filename</I>[<B>.lef</B>]
<DT> [<I>filename</I>] <B>-import</B>
<DD> Read a LEF file. Import standard cells from <TT>.mag</TT>
files
<DT> <B>write</B> [<I>cell</I>]
<DD> Write LEF for the current or indicated cell.
<DT> <B>writeall</B>
<DD> Write all cells including the top-level cell. This might
be appropriate if the top-level cell is a compendium of
standard cells.
<DT> <B>writeall -notop</B>
<DD> write all subcells of the top-level cell, but not the top-level
cell itself. This is appropriate for generating a LEF library
from a layout, for which the layout itself would be written to
a DEF file.
<DT> <B>help</B>
<DD> Print help information
</DL>
</BLOCKQUOTE>
</BLOCKQUOTE>
<H3>Summary:</H3>
<BLOCKQUOTE>
The <B>lef</B> command writes LEF-format files, which are files
containing technology information and information about the content
of standard cells. It is used in conjunction with the <B>def</B>
command to read databases of routed digital standard-cell layouts.
The <TT>.lef</TT> file shares some information with the technology
file in <B>magic</B>. At a minimum, to read <TT>.lef</TT> files
from third-party sources, the technology file should have a
<B>lef</B> section that maps magic layers to layer names that are
found in the <TT>.lef</TT> and <TT>.def</TT> files. Without
this information, <B>magic</B> will attempt to make an educated
guess about the routing layers, which normally will be named
in an obvious manner such as "metal1", "metal2", etc. The
technology file section may be necessary to handle more complicated
input such as obstruction layers. Most other aspects of a
technology will be contained within the <TT>.lef</TT> file.
When writing <TT>.lef</TT> files, <B>magic</B> will use internal
layer names for the routing layers if no other information is
present in the <B>lef</B> section of the technology file. <P>
Because the <B>lef</B> format allows standard cells to be minimally
defined (for purposes of protecting intellectual property), often
the <TT>.lef</TT> file contains no actual layout information for
the standard cells. <B>magic</B> provides a command option
"<B>-import</B>". When specified, for each macro cell in the
input <TT>.lef</TT> file, <B>magic</B> will look for a <TT>.mag</TT>
file of the same name. If found, it will be loaded and used in
preference to the definition in the <TT>lef</TT> file. <P>
Magic uses the <B>port</B> mechanism for labels to determine
what are the standard cells in a design. All cells containing
<B>port</B> labels will be considered standard cells when writing
a <TT>.lef</TT> file. Ports retain various bits of information
used by the LEF/DEF definition, including the port use and
direction. See the <B>port</B> documentation for more information.<P>
Macro cell properties common to the LEF/DEF definition but that
have no corresponding database interpretation in <B>magic</B>
are retained using the cell <B>property</B> method in <B>magic</B>.
There are specific property names associated with the LEF format.
These are as follows:
<DL>
<DT> <B>LEFclass</B>
<DD> Corresponds to the value of <B>CLASS</B> for a macro
cell in the LEF format.
<DT> <B>LEFsource</B>
<DD> Corresponds to the value of <B>SOURCE</B> for a macro
cell in the LEF format.
<DT> <B>LEFsymmetry</B>
<DD> Corresponds to the vlaue of <B>SYMMETRY</B> for a macro
cell in the LEF format.
</DL>
Normally, when importing a LEF/DEF layout into <B>magic</B>, one
will first execute a <B>lef read</B> command followed by a
<B>def read</B> command. Likewise, when writing a layout, one
will first execute a <B>lef writeall -notop</B> command followed
by a <B>def write</B> command.
</BLOCKQUOTE>
<H3>Implementation Notes:</H3>
<BLOCKQUOTE>
<B>lef</B> is implemented as a built-in command in <B>magic</B>.
Only the critical portion of the LEF syntax has been implemented.
In particular, simulation-specific properties of the technology
and of macro cells are not implemented.
</BLOCKQUOTE>
<H3>See Also:</H3>
<BLOCKQUOTE>
<A HREF=def.html><B>def</B></A> <BR>
<A HREF=port.html><B>port</B></A> <BR>
<A HREF=property.html><B>property</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 7, 2004 at 1:43am <P>
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