markdown/OR_docs/tools/src/ppl/README.md

Pin Placer

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

- Parameters in square brackets `[-param param]` are optional.
- Parameters without square brackets `-param2 param2` are required.

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]

Options

Switch Name	Description
-layer	The single top-most routing layer of the placement grid.
-x_step, -y_step	The distance (in microns) between each valid position on the grid in the x- and y-directions, respectively.
-region	The {llx, lly, urx, ury} region of the placement grid (in microns). If the * is specified, the region will be the entire die area.
-size	The width and height (in microns) 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.
-pin_keepout	The boundary (in microns) around existing routing obstructions that the pins should avoid; this defaults to the layer minimum spacing.

Face-to-Face direct-bonding IOs

The define_pin_shape_pattern command can be used to place pins in any metal layer with the minimum allowed spacing to facilitate 3DIC integration of chips using face-to-face packaging technologies. These technologies include micro bumps and hybrid bonding for high density face-to-face interconnect.

Set IO Pin Constraints

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.

You can use the set_io_pin_constraint command to restrict pins to the pin placement grid created with the define_pin_shape_pattern command.

It is possible to use the -region, -group and -order arguments together per set_io_pin_constraint call, but the -mirrored_pins argument should be called alone.

set_io_pin_constraint 
    [-direction direction]
    [-pin_names names]
    [-region edge:interval]
    [-mirrored_pins names]
    [-group]
    [-order]

Options

Switch Name	Description
-direction	Pin direction (input, output, inout, or feedthrough).
-pin_names	List of names. Only one of (-direction, -pin_names) should be used in a single call for the set_io_pin_constraint command.
-region	Syntax is -region edge:interval. The edge values are (top|bottom|left|right). The interval can be the whole edge with the wildcard * value or a range of values.
-mirrored_pins	List of pins that sets pairs of pins that will be symmetrically placed in the vertical or the horizontal edges. The number of pins in this list must be even. For example, in set_io_pin_constraint -mirrored_pins {pin1 pin2 pin3 pin4 pin5 pin6}, the pins pin1 and pin2 will be placed symmetrically to each other. Same for pin3 and pin4, and for pin5 and pin6.
-group	Flag places together on the die boundary the pin list defined in -pin_names, similar to the -group_pins option on the place_pins command.
-order	Flag places the pins ordered in ascending x/y position and must be used only when -group is also used.

The edge values are (up, top, bottom, left, right), where up is the grid 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. The region is defined in microns.
• -region up:* to restrict the pins into the entire region of the grid.

The up option is only available when the pin placement grid is created with the define_pin_shape_pattern command.

Clear IO Pin Constraints

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

clear_io_pin_constraints

Set Pin Length

The set_pin_length command defines the length of all vertical and horizontal pins.

set_pin_length 
    [-hor_length h_length]
    [-ver_length v_length]

Options

Switch Name	Description
-hor_length	The length (in microns) of the horizontal pins.
-ver_length	The length (in microns) of the vertical pins.

The default length of the pins is the minimum length necessary to respect the minimum area defined in the routing layer they were placed. The width of the pins is the minimum width defined in the routing layer.

Set Pin Length Extension

The set_pin_length_extension command defines the an extension of the length of all vertical and horizontal pins. Note that this command may generate pins partially outside the die area.

set_pin_length_extension 
    [-hor_extension h_extension]
    [-ver_extension v_extension]

Options

Switch Name	Description
-hor_extension	The length (in microns) for the horizontal pins.
-ver_extension	The length (in microns) for the vertical pins.

Set Pin Thickness Multiplier

The set_pin_thick_multiplier command defines a multiplier for the thickness of all vertical and horizontal pins.

set_pin_thick_multiplier 
    [-hor_multiplier h_mult]
    [-ver_multiplier v_mult]

Options

Switch Name	Description
-hor_multiplier	The thickness multiplier for the horizontal pins.
-ver_multiplier	The thickness multiplier for the vertical pins.

Set Simulated Annealing

The set_simulated_annealing command defines the parameters for simulated annealing pin placement.

set_simulated_annealing
    [-temperature temperature]
    [-max_iterations iter]
    [-perturb_per_iter perturbs]
    [-alpha alpha]

Options

Switch Name	Description
-temperature	Temperature parameter. The default value is 1.0, and the allowed values are floats [0, MAX_FLOAT].
-max_iterations	The maximum number of iterations. The default value is 2000, and the allowed values are integers [0, MAX_INT].
-perturb_per_iter	The number of perturbations per iteration. The default value is 0, and the allowed values are integers [0, MAX_INT].
-alpha	The temperature decay factor. The default value is 0.985, and the allowed values are floats (0, 1].

Simulated Annealing Debug Mode

The simulated_annealing_debug command allows you to debug the simulated annealing pin placement with a pause mode.

simulated_annealing_debug
    [-iters_between_paintings iters]
    [-no_pause_mode no_pause_mode]

Options

Switch Name	Description
-iters_between_paintings	Determines the number of iterations between updates.
-no_pause_mode	Print solver state every second based on iters_between_paintings.

Place specific Pin

The place_pin command places a specific pin in the specified location with the specified size. It is recommended that individual pins be placed before the place_pins command, as the routing tracks occupied by these individual pins will be blocked, preventing overlaps.

To place an individual pin:

place_pin 
    -pin_name pin_name
    -layer layer
    -location {x y}
    [-pin_size {width height}]
    [-force_to_die_boundary]
    [-placed_status]

Options

Switch Name	Description
-pin_name	The name of a pin of the design.
-layer	The routing layer where the pin is placed.
-location	The center of the pin (in microns).
-pin_size	The width and height of the pin (in microns).
-force_to_die_boundary	When this flag is enabled, the pin will be snapped to the nearest routing track, next to the die boundary.

Place all Pins

The place_pins command places all pins together. Use the following command to perform pin placement:

Developer arguments:

• -random, -random_seed

place_pins 
    -hor_layers h_layers
    -ver_layers v_layers
    [-random_seed seed]
    [-random]
    [-corner_avoidance length]
    [-min_distance distance]
    [-min_distance_in_tracks]
    [-exclude region]
    [-group_pins pin_list]
    [-annealing]
    [-write_pin_placement file_name]

Options

Switch Name	Description
-hor_layers	The layers to create the metal shapes of pins placed in horizontal tracks. It can be a single layer or a list of layer names.
-ver_layers	The layers to create the metal shapes of pins placed in vertical tracks. It can be a single layer or a list of layer names.
-corner_avoidance	The distance (in microns) from each corner within which pin placement should be avoided.
-min_distance	The minimum distance between pins on the die boundary. This distance can be in microns (default) or in number of tracks between each pin. The default value is the length of two routing tracks between each pin.
-min_distance_in_tracks	Flag that allows setting the min distance in number of tracks instead of microns.
-exclude	A region where pins cannot be placed. Either `top
-group_pins	A list of pins to be placed together on the die boundary.
-annealing	Flag to enable simulated annealing pin placement.
-write_pin_placement	A file with the pin placement generated in the format of multiple calls for the place_pin command.

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.

Developer Arguments

Switch Name	Description
-random_seed	Specify the seed for random operations.
-random	When this flag is enabled, the pin placement is random.

Write Pin Placement

The write_pin_placement command writes a file with the pin placement in the format of multiple calls for the place_pin command:

write_pin_placement 
    file_name

Options

Switch Name	Description
file_name	The name of the file with the pin placement.

Useful Developer Commands

If you are a developer, you might find these useful. More details can be found in the source file or the swig file.

Command Name	Description
parse_edge	Parse edge (top/bottom/left/right).
parse_direction	Parse direction.
parse_excludes_arg	Parse excluded arguments.
parse_group_pins_arg	Parse group pins arguments.
parse_layer_name	Parse layer name.
parse_pin_names	Parse pin names.
get_edge_extreme	Get extremes of edge.
exclude_intervals	Set exclude interval.
add_pins_to_constraint	Add pins to constrained region.
add_pins_to_top_layer	Add pins to top layer.

Example scripts

Example scripts of ppl running on a sample design of gcd as follows:

./test/gcd.tcl

Regression tests

There are a set of regression tests in ./test. For more information, refer to this section.

Simply run the following script:

./test/regression

Limitations

References

• This code depends on Munkres.

FAQs

Check out GitHub discussion about this tool.

License

BSD 3-Clause License. See LICENSE file.