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SIM(5)			      File Formats Manual			SIM(5)

       sim - format of .sim files read by esim,	crystal, etc.

       The  simulation	tools crystal(1) and esim(1) accept a circuit descrip-
       tion in .sim format.  There is a	single .sim file for the  entire  cir-
       cuit,  unlike  Magic's  ext(5) format in	which there is a .ext file for
       every cell in a hierarchical design.

       A .sim file consists of a series	of lines, each of which	begins with  a
       key letter.  The	key letter beginning a line determines how the remain-
       der of the line is interpreted.	The following are the list of key let-
       ters understood.

       | units:	s  tech: tech format: MIT|LBL|SU
	      If  present,  this  must be the first line in the	.sim file.  It
	      identifies the technology	of this	circuit	as tech	 and  gives  a
	      scale factor for units of	linear dimension as s.	All linear di-
	      mensions appearing in the	.sim file are multiplied by s to  give
	      centimicrons.  The  format  field	signifies the sim variant. MIT
	      and SU are compatible and	understood by all tools. LBL is	under-
	      stood only by gemini(1).

       type  g	s  d  l	 w  x  y  g=gattrs  s=sattrs  d=dattrs
	      Defines  a transistor of type type.  Currently, type may be e or
	      d	for NMOS, or p or n for	CMOS.  The name	of the node  to	 which
	      the  gate, source, and drain of the transistor are connected are
	      given by g, s, and d respectively.  The length and width of  the
	      transistor  are  l and w.	 The next two tokens, x	and y, are op-
	      tional.  If present, they	give the location of  a	 point	inside
	      the  gate	 region	 of the	transistor.  The last three tokens are
	      the attribute lists for the transistor gate, source, and	drain.
	      If no attributes are present for a particular terminal, the cor-
	      responding attribute list	may be absent (i.e, there may be no g=
	      field at all).  The attribute lists gattrs, etc. are comma-sepa-
	      rated lists of labels.  The label	names should not  include  any
	      spaces,  although	 some tools can	accept label names with	spaces
	      if they are enclosed in double quotes.   In  version  6.4.5  and
	      later the	default	format produced	by ext2sim is SU. In this for-
	      mat the attribute	of the gate starting with S_ is	the  substrate
	      node of the fet. The attributes of the gate, and source and sub-
	      strate starting with A_, P_ are the area and  perimeter  (summed
	      for  that	 node only once) of the	source and drain respectively.
	      This addition to the format is backwards compatible.

       C n1 n2 cap
	      Defines a	capacitor between nodes	n1 and n2.  The	value  of  the
	      capacitor	 is  cap femtofarads.  NOTE: since many	analysis tools
	      compute transistor gate capacitance themselves from the transis-
	      tor's  area  and	perimeter,  the	capacitance between a node and
	      substrate	(GND!) normally	does not include the capacitance  from
	      transistor  gates	 connected to that node.  If the .sim file was
	      produced by ext2sim(1), check the	technology file	that was  used
	      to  produce  the	original  .ext files to	see whether transistor
	      gate capacitance is included  or	excluded;  see	``Magic	 Main-
	      tainer's Manual #2: The Technology File''	for details.

       R node res
	      Defines the lumped resistance of node node to be res ohms.  This
	      construct	is only	interpreted by a few programs.

       r node1 node2 res
	      Defines an explicit resistor between nodes node1	and  node2  of
	      resistance  res  ohms.   This construct is only interpreted by a
	      few programs.

       N node darea dperim parea pperim	marea mperim
	      As an alternative	to computed capacitances,  some	 tools	expect
	      the  total perimeter and area of the polysilicon,	diffusion, and
	      metal in each node to be reported	in the .sim file.  The N  con-
	      struct  associates diffusion area	darea (in square centimicrons)
	      and diffusion perimeter dperim (in centimicrons) with node node,
	      polysilicon  area	 parea	and  perimeter	pperim,	and metal area
	      marea and	perimeter mperim.  This	construct is technology	depen-
	      dent and obsolete.

       A node attr
	      Associates attribute attr	for node node.	The string attr	should
	      contain no blanks.

       = node1 node2
	      Each node	in a .sim file is named	implicitly by having it	appear
	      in  a transistor definition.  All	node names appearing in	a .sim
	      file are assumed to be distinct.	Some tools, such  as  esim(1),
	      recognize	 aliases  for  node names.  The	= construct allows the
	      name node2 to be	defined	 as  an	 alias	for  the  name	node1.
	      Aliases  defined	by means of this construct may not appear any-
	      where else in the	.sim file.

       crystal(1), esim(1), ext2sim(1),	sim2spice(1), ext(5)

4th Berkeley Distribution						SIM(5)


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