NAME

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

DESCRIPTION

       The  simulation  tools crystal(1) and esim(1) accept a circuit description in .sim format.
       There is a single .sim file for the entire circuit, 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 remainder of the line is interpreted.   The
       following are the list of key letters 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 dimensions 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 understood 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  optional.
              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
              corresponding attribute list may be absent (i.e, there may be no g= field at  all).
              The  attribute  lists  gattrs, etc. are comma-separated 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 format the attribute of the  gate
              starting  with S_ is the substrate node of the fet. The attributes of the gate, and
              source and substrate 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 transistor'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  Maintainer'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  construct  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 dependent 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 anywhere else in the .sim file.

SEE ALSO

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