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)

4th Berkeley Distribution                                                                                 SIM(5)