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 description 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
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 centimi-
crons. The format field signifies the sim variant. MIT and SU are compatible and understood by all tools. LBL is understood only by
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 transis-
tor 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 pro-
duced 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 com-
pute 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 pro-
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 diffu-
sion 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
crystal(1), esim(1), ext2sim(1), sim2spice(1), ext(5)
4th Berkeley Distribution SIM(5)