Initialize Floorplan#

This tool initializes floorplan constraints, die/core area, and makes tracks.

Commands#

Note

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

Initialize Floorplan#

Do note that there are two ways of setting the floorplan dimensions. The user can either specify manually die/core area, or specify the utilization/aspect ratio. If you set both, unexpected behaviour might occur.

Method 1: Automatic die size calculation Example: initialize_floorplan -utilization 70 -aspect_ratio 1.0 -core_space 0.0 -sites FreePDK45_38x28_10R_NP_162NW_34O
Method 2: Set die/core area Example: initialize_floorplan -die_area 0 0 2000 2000 -core_area 100 100 1900 1900 -sites FreePDK45_38x28_10R_NP_162NW_34O`

The die area and core area used to write ROWs can be specified explicitly with the -die_area and -core_area arguments. Alternatively, the die and core areas can be computed from the design size and utilization as shown below:

The -site argument determines the basic single-height rows to make. For a hybrid row design the site should have a row pattern. Any sites referenced by an instance in the netlist will also have rows constructed for them.

Additional sites are specified if you wish to have rows for a site that is not used in the nelist but may be needed later. For example, you might not have any double height cells in the incoming netlist but you expect some to be generated by flop clustering later in the flow.

Example computation:

core_area = design_area / (utilization / 100)
core_width = sqrt(core_area / aspect_ratio)
core_height = core_width * aspect_ratio
core = ( core_space_left, core_space_bottom )
      ( core_space_left + core_width, core_space_bottom + core_height )
die =  ( 0, 0 )
      ( core_width + core_space_left + core_space_right,
        core_height + core_space_bottom + core_space_top )

initialize_floorplan
  (-die_area {llx lly urx ury | x1 y1 x2 y2 ...} -core_area {llx lly urx ury | x1 y1 x2 y2 ...}) | (-utilization util -core_space (space | {bottom top left right}) [-aspect_ratio ratio])
  -site site_name
  [-additional_sites site_names]
  [-flip_sites site_names]
  [-gap space]
  [-row_parity NONE|EVEN|ODD]

Options#

Switch Name	Description
`-core_area`	Core area coordinates in microns. Either a rectangle as `{llx lly urx ury}`, or a rectilinear polygon as a list of vertex coordinates `{x1 y1 x2 y2 ...}`. See Rectilinear Floorplans.
`-core_space`	Space around the core in microns. Allowed values are either one value for all margins or a set of four values, one for each margin. The order of the four values are: `{bottom top left right}`.
`-die_area`	Die area coordinates in microns. Either a rectangle as `{llx lly urx ury}`, or a rectilinear polygon as a list of vertex coordinates `{x1 y1 x2 y2 ...}`. See Rectilinear Floorplans.
`-site`	Site name.
`-utilization`	Percentage utilization. Allowed values are `double` in the range `(0-100]`.
`[-additional_sites]`	Tcl list of sites to make rows for (e.g. `{SITEXX, SITEYY}`)
`[-aspect_ratio]`	Ratio \(\frac{height}{width}\). The default value is `1.0` and the allowed values are floats `[0, 1.0]`.
`[-flip_sites]`	Flip the orientations of rows matching these sites. Sites listed under this option will create `FS`-oriented rows at even indices and `N`-oriented rows at odd ones, and vice versa for sites not listed under this option. (e.g. `{SITEXX, SITEYY}`)
`[-gap]`	Space between power domains in microns. The default value is 6 times the minimum site height.
`[-row_parity]`	Snap to either an odd (`ODD`) or even (`EVEN`) number of rows. Defaults to `NONE` (no constraint on parity).

Rectilinear Floorplans#

The initialize_floorplan command supports non-rectangular die and core outlines (e.g. L-shapes, T-shapes, or arbitrary rectilinear polygons). Rectilinear mode is selected automatically when -die_area is given more than four coordinates. When rectilinear mode is used, -core_area must also be specified as a polygon (it is not derived from -utilization, -aspect_ratio, or -core_space).

Example: an L-shaped die with a matching L-shaped core, with a 20 micron margin between them.

initialize_floorplan \
  -die_area  {0 0   200 0   200 100   100 100   100 200   0 200} \
  -core_area {20 20  180 20  180 80   80 80     80 180    20 180} \
  -site FreePDK45_38x28_10R_NP_162NW_34O

Rows are generated only inside the polygonal core, respecting its rectilinear edges.

Polygon Vertex Rules#

Coordinates are in microns, listed as {x1 y1 x2 y2 ... xN yN}.
The vertex count must be even (each x paired with a y).
Exactly 4 coordinates are interpreted as a rectangle. A polygon must have more than 4 coordinates and at least 4 vertices (8 coordinates).
Edges must be axis-aligned (rectilinear): consecutive vertices must share either an x or a y coordinate.
The die polygon must fully contain the core polygon.

Make Tracks#

The initialize_floorplan command removes existing tracks. Use the make_tracks command to add routing tracks to a floorplan.

make_tracks 
    [layer]
    [-x_offset x_offset]
    [-y_offset y_offset]
    [-x_pitch x_pitch]
    [-y_pitch y_pitch]

Options#

Switch Name	Description
`[layer]`	Select layer name to make tracks for. Defaults to all layers.
`[-x_offset]`, `[-y_offset]`	If set, overrides the LEF technology x-/y- offset. Use the same unit as in the LEFT file.
`[-x_pitch]`, `[-y_pitch]`	If set, overrides the LEF technology x-/y- pitch. Use the same unit as in the LEF file.

Make Rows#

The make_rows command removes existing rows. Use the make_rows command to add rows to an existing floorplan. Useful, if your floorplan is stored as a floorplan def without rows.

make_rows
  (-core_area {llx lly urx ury}) | (-core_space (space | {bottom top left right}))
  -site site_name
  [-additional_sites site_names]
  [-flip_sites site_names]
  [-gap space]
  [-row_parity NONE|EVEN|ODD]

Options#

Switch Name	Description
`-core_area`	Core area coordinates in microns (lower left x/y and upper right x/y coordinates).
`-core_space`	Space around the core in microns. Allowed values are either one value for all margins or a set of four values, one for each margin. The order of the four values are: `{bottom top left right}`.
`-site`	Site name.
`[-additional_sites]`	Tcl list of sites to make rows for (e.g. `{SITEXX, SITEYY}`)
`[-flip_sites]`	Flip the orientations of rows matching these sites. Sites listed under this option will create `FS`-oriented rows at even indices and `N`-oriented rows at odd ones, and vice versa for sites not listed under this option. (e.g. `{SITEXX, SITEYY}`)
`[-gap]`	Space between power domains in microns. The default value is 6 times the minimum site height.
`[-row_parity]`	Snap to either an odd (`ODD`) or even (`EVEN`) number of rows. Defaults to `NONE` (no constraint on parity).

Insert tieoff cells#

This comamnd inserts tiecells.

insert_tiecells 
    [-prefix inst_prefix]
    tie_pin

Options#

Switch Name	Description
`[-prefix]`	Used to control the prefix of the new tiecell names. This will default to `TIEOFF_`.
`tie_pin`	Indicates the master and port to use to tie off nets. For example, `LOGIC0_X1/Z` for the Nangate45 library, where `LOGIC0_X1` is the master and `Z` is the output port on the master.

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
`microns_to_mfg_grid`	Convert microns to manufacturing grid DBU.

Example scripts#

Example scripts on running ifp for a sample design of mpd_top are as follows:

./test/upf_test.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

Initialize Floorplan

Contents

Initialize Floorplan#

Commands#

Initialize Floorplan#

Options#

Rectilinear Floorplans#

Polygon Vertex Rules#

Make Tracks#

Options#

Make Rows#

Options#

Insert tieoff cells#

Options#

Useful Developer Commands#

Example scripts#

Regression tests#

Limitations#

FAQs#

License#