OpenROAD

ioPlacer¶

Place pins on the boundary of the die on the track grid to minimize net wirelengths. Pin placement also creates a metal shape for each pin using min-area rules.

For designs with unplaced cells, the net wirelength is computed considering the center of the die area as the unplaced cells’ position.

Commands¶

Place All Pins¶

Use the following command to perform pin placement:

place_pins [-hor_layers <h_layers>]
           [-ver_layers <v_layers>]
           [-random_seed <seed>]
           [-exclude <interval>]
           [-random]
           [-group_pins <pins>]
           [-corner_avoidance <length>]
           [-min_distance <distance>]
           [-min_distance_in_tracks]

-hor_layers (mandatory). Specify the layers to create the metal shapes of pins placed in horizontal tracks. Can be a single layer or a list of layer names.
-ver_layers (mandatory). Specify the layers to create the metal shapes of pins placed in vertical tracks. Can be a single layer or a list of layer names.
-random_seed. Specify the seed for random operations.
-exclude. Specify an interval in one of the four edges of the die boundary where pins cannot be placed. Can be used multiple times.
-random. When this flag is enabled, the pin placement is random.
-group_pins. Specify a list of pins to be placed together on the die boundary.
-corner_avoidance distance. Specify the distance (in microns) from each corner within which pin placement should be avoided.
-min_distance distance. Specify the minimum distance between pins on the die boundary. This distance can be in microns (default) or in number of tracks between each pin.
-min_distance_in_tracks. Flag that allows setting the min distance in number of tracks instead of microns.

The exclude option syntax is -exclude edge:interval. The edge values are (top|bottom|left|right). The interval can be the whole edge, with the * value, or a range of values. For example, in place_pins -hor_layers metal2 -ver_layers metal3 -exclude top:* -exclude right:15-60.5 -exclude left:*-50 three intervals are excluded: the whole top edge, the right edge from 15 microns to 60.5 microns, and the left edge from its beginning to 50 microns.

Place Individual Pin¶

place_pin [-pin_name <pin_name>]
          [-layer <layer>]
          [-location <{x y}>]
          [-pin_size <{width height}>]

The place_pin command places a specific pin in the specified location, with the specified size.

-pin_name option is the name of a pin of the design.
-layer defines the routing layer where the pin is placed.
-location defines the center of the pin.
-pin_size option defines the width and height of the pin.

Define Pin Shape Pattern¶

The define_pin_shape_pattern command defines a pin placement grid on the specified layer. This grid has positions inside the die area, not only at the edges of the die boundary.

define_pin_shape_pattern [-layer <layer>]
                         [-x_step <x_step>]
                         [-y_step <y_step>]
                         [-region <{llx lly urx ury}>]
                         [-size <{width height}>]
                         [-pin_keepout <dist>]

The -layer option defines a single top-most routing layer of the placement grid.
The -region option defines the {llx, lly, urx, ury} region of the placement grid.
The -x_step and -y_step options define the distance between each valid position on the grid, in the x- and y-directions, respectively.
The -size option defines the width and height of the pins assigned to this grid. The centers of the pins are placed on the grid positions. Pins may have half of their shapes outside the defined region.
The -pin_keepout option defines the boundary (microns) around existing routing obstructions that the pins should avoid; this defaults to the layer minimum spacing.

Set IO Pin Constraint¶

The set_io_pin_constraint command sets region constraints for pins according to the pin direction or the pin name. This command can be called multiple times with different constraints. Only one condition should be used for each command call.

The -direction argument is the pin direction (input, output, inout, or feedthrough). The -pin_names argument is a list of names. The -region syntax is the same as that of the -exclude syntax.

Note that if you call define_pin_shape_pattern before set_io_pin_constraint, the edge values are (up, top, bottom, left, right). Where up relates to the layer created by define_pin_shape_pattern. To restrict pins to the pin placement grid defined with define_pin_shape_pattern use:

-region up:{llx lly urx ury} to restrict the pins into a specific region in the grid
-region up:* to restrict the pins into the entire region of the grid.

set_io_pin_constraint -direction <direction>
                      -pin_names <names>
                      -region <edge:interval>

Clear IO Pin Constraints¶

The clear_io_pin_constraints command clears all the previously-defined constraints and pin shape patterns created with define_pin_shape_pattern.

clear_io_pin_constraints

Example scripts¶

Regression tests¶

Limitations¶

External references¶

This code depends on Munkres.

FAQs¶

Check out GitHub discussion about this tool.

License¶

BSD 3-Clause License. See LICENSE file.

Table Of Contents

ioPlacer

Initialize Floorplan

ICeWall