Pins and Timing Constraints

Pins and Constraints

Pins (.sitspins)

This file contains the following information for each net present in the netlist (each net is assumed to be uniquely identifiable by a name).

    -- the set of pins, each pin uniquely identified by a name
    -- the x,y information for each pin
    -- the direction of the pin -- input, output or input/output

The format of the file is

     NET <netname>
       PIN <pin_name> <x> <y> <I/O/IO>
       PIN <pin_name> <x> <y> <I/O/IO>
       .
       .
       PIN <pin_name> <x> <y> <I/O/IO>
     END

# Beginning of next net

     NET <netname>
       PIN <pin_name> <x> <y> <I/O/IO>
       PIN <pin_name> <x> <y> <I/O/IO>
       .
       .
       PIN <pin_name> <x> <y> <I/O/IO>
     END

Format description

NET and END mark the beginning and end of a specific net
netname specifies the name of the net
PIN specifies the beginning of a new PIN
pin_name specifies the name of the current pin
pin names are unique within a given net, but can be duplicated over multiple nets
x,y specify the x and y positions of the current pin
the last field on a PIN line specifies the pin type -- I for input pin, O for output pin and IO for a bidirectional pin
# marks the beginning of a comment line and blank lines in the input file are ignored

Format specifications

netname, pin_name are alphanumeric strings with elements taken from [a-zA-Z0-9]
keywords NET, END and PIN should be in upper case
x and y positions are integers (long) giving the pin position in micron units

example

Pins to layer assignment (.sitslayer)

This file assigns pins to specified layers. It is recommended to read .sitspins file first, and also to read the file describing layers.

    NET <netname>
      [ DEFAULT_LAYER <layerID> ]
      PIN <name> <layerID>
      PIN <name> <layerID>
      .
      .
      PIN <name> <layerID>
    END

Format description

NET and END mark the beginning and ending of a net
DEFAULT_LAYER specifies the default layer ID value for all pins that are specified in corresponding .sitspins file but not mentioned here.

Format specifications

pin and net names should comply with the name specification declared in the .sitspins section
<layerID> is an integer value specifying layer ID

example

Pin polarity (.pol)

This file assigns input and output signal polarity for each pin. It is recommended to read .sitspins file first.

    NET <netname>
      [ DEFAULT_POL <0/1> ]
      PIN <name> <0/1>
      PIN <name> <0/1>
      .
      .
      PIN <name> <0/1>
    END

Format description

NET and END mark the beginning and ending of a net
DEFAULT_POL specifies the default pin polarity value for all pins that are specified in corresponding .sitspins file but not mentioned here.

Format specifications

pin and net names should comply with the name specification declared in the .sitspins section
0 - Noninverted, 1 - Inverted

example

Pin input capacitance (.cap)

This file assigns input capacitance for each pin that is specified as an input pin. It is recommended to read .sitspins file first.

    NET <netname>
      [ DEFAULT_CAP <cap> ]
      PIN <name> <cap>
      PIN <name> <cap>
      .
      .
      PIN <name> <cap>
    END

Format description

NET and END mark the beginning and ending of a net
DEFAULT_CAP specifies the default pin input capacitance for all pins that are specified in corresponding .sitspins file as input pins but not mentioned here.

Format specifications

pin and net names should comply with the name specification declared in the .sitspins section
<cap> is floating point value in pF

example

Pin input slew rise and fall time (.slew)

This file assigns input slew rise and fall time for each pin that is specified as an input pin. It is recommended to read .sitspins file first.

    NET <netname>
      [ DEFAULT_SLEW_RISE <slew_rise> ]
      [ DEFAULT_SLEW_FALL <slew_fall> ]
      PIN <name> <slew_rise> <slew_fall>
      PIN <name> <slew_rise> <slew_fall>
      .
      .
      PIN <name> <slew_rise> <slew_fall>
    END

Format description

NET and END mark the beginning and ending of a net
DEFAULT_SLEW_RISE and DEFAULT_SLEW_FALL specify the default pin input slew rise and fall time for all pins that are specified in corresponding .sitspins file as input pins but not mentioned here.

Format specifications

pin and net names should comply with the name specification declared in the .sitspins section
<slew_rise> and <slew_fall> are floating point values in pico seconds

example

Pin noise margin (.noise)

This file assigns noise margin for each pin that is specified as an input pin. It is recommended to read .sitspins file first.

    NET <netname>
      [ DEFAULT_NOISE <noise_margin> ]
      PIN <name> <noise_margin>
      PIN <name> <noise margin>
      .
      .
      PIN <name> <noise margin>
    END

Format description

NET and END mark the beginning and ending of a net
DEFAULT_NOISE specifies the default pin noise margin for all pins that are specified in corresponding .sitspins file as input pins but not mentioned here.

Format specifications

pin and net names should comply with the name specification declared in the .sitspins section
<noise_margin> is floating point value in pico seconds

example

Pin required arrival time constraint (.rat)

This file assigns required arrival time constraints for each pin that is specified as an input pin. It is recommended to read .sitspins file first.

    NET <netname>
      SOURCE <pin_name>
        [ DEFAULT_RAT <rat> ]
        PIN <pin_name> <rat>
        PIN <pin_name> <rat>
        .
        .
        PIN <pin_name> <rat>
      END

# another source

      SOURCE <pin_name>
        [ DEFAULT_RAT <rat> ]
        PIN <pin_name> <rat>
        PIN <pin_name> <rat>
        .
        .
        PIN <pin_name> <rat>
      END
    END

Format description

NET and END mark the beginning and ending of a net
DEFAULT_RAT specifies the default pin required arrival time for all pins that are specified in corresponding .sitspins file as input pins but not mentioned in scope within the current source pin
required arrival times are defined for all sinks in respect to the specified driver in its SOURCE block

Format specifications

pin and net names should comply with the name specification declared in the .sitspins section
<rat> is floating point value in pico seconds

example

Source pin parameters (.src)

This file specifies intrindic delay and output resistance for each pin that is specified as an output pin. It is recommended to read .sitspins file first.

    NET <netname>
      PIN <name> <int_delay> <out_res>
      PIN <name> <int_delay> <out_res>
      .
      .
      PIN <name> <int_delay> <out_res>
    END

Format description

NET and END mark the beginning and ending of a net

Format specifications

pin and net names should comply with the name specification declared in the .sitspins section
<int_delay> is floating point value in pico seconds
<out_res> is floating point value in Ohms

example

Buffer stations (.bufstat)

This file specifies buffer stations (i.e. feisible buffer locations) as union of rectangles at specified layer. It is recommended to first read the file desribing layers.

    BUFSTAT <x1> <y1> <x2> <y2> <layerID>
    BUFSTAT <x1> <y1> <x2> <y2> <layerID>
    .
    .
    BUFSTAT <x1> <y1> <x2> <y2> <layerID>

Format description

BUFSTAT is a keyword specifying buffer station
<x1> <y1> <x2> <y2> represent the coordinates of opposite corners of a bounding rectangle

Format specifications

layerID should comply with the layers declared in the layers section
<x1> <y1> <x2> <y2> are floating point values in microns
<layerID> is an integer value specifying layer ID

example

Buffer blockages (.bufblock)

This file specifies buffer blockages as union of rectangles at specified layer. It is recommended to first read the file desribing layers.

    BUFBLOCK <x1> <y1> <x2> <y2> <layerID>
    BUFBLOCK <x1> <y1> <x2> <y2> <layerID>
    .
    .
    BUFBLOCK <x1> <y1> <x2> <y2> <layerID>

Format description

BUFBLOCK is a keyword specifying buffer blockage
<x1> <y1> <x2> <y2> represent the coordinates of opposite corners of a bounding rectangle

Format specifications

layerID should comply with the layers declared in the layers section
<x1> <y1> <x2> <y2> are floating point values in microns
<layerID> is an integer value specifying layer ID

example

Routing blockages (.routblock)

This file specifies routing blockages as union of rectangles at specified layer. It is recommended to first read the file desribing layers.

    ROUTBLOCK <x1> <y1> <x2> <y2> <layerID>
    ROUTBLOCK <x1> <y1> <x2> <y2> <layerID>
    .
    .
    ROUTBLOCK <x1> <y1> <x2> <y2> <layerID>

Format description

ROUTBLOCK is a keyword specifying routing blockage
<x1> <y1> <x2> <y2> represent the coordinates of opposite corners of a bounding rectangle

Format specifications

layerID should comply with the layers declared in the layers section
<x1> <y1> <x2> <y2> are floating point values in microns
<layerID> is an integer value specifying layer ID

example

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