OpenROAD API

OpenROAD can be run using Tcl, and Python (limited support). The following commands are used to read and write design data.

.. tabs::

   .. code-tab:: tcl

      read_lef [-tech] [-library] filename
      read_def filename
      write_def [-version 5.8|5.7|5.6|5.5|5.4|5.3] filename
      read_verilog filename
      write_verilog filename
      read_db filename
      write_db filename
      write_abstract_lef filename

   .. code-tab:: python
   
      # read_verilog, write_verilog and write_abstract_lef are not supported in Python.
      read_lef(db: odb.dbDatabase, path: str) -> odb.dbLib
      read_def(tech: odb.dbTech, path: str) -> odb.dbChip
      write_def(block: dbBlock, path: str, version: Optional[odb.defout.Version]) -> int
      read_db(db: odb.dbDatabase, db_path: str) -> odb.dbDatabase
      write_db(db: odb.dbDatabase, db_path: str) -> int

Use the Tcl source command to read commands from a file.

.. tabs::

   .. code-tab:: tcl

      source [-echo] file

   .. code-tab:: py

      # Source is not supported in Python.
      # Instead run this at the start:
      openroad -python script.py

If an error is encountered in a command while reading the command file, then the error is printed and no more commands are read from the file. If file_continue_on_error is 1 then OpenROAD will continue reading commands after the error.

If exit_on_error is 1 then OpenROAD will exit when it encounters an error.

OpenROAD can be used to make a OpenDB database from LEF/DEF, or Verilog (flat or hierarchical). Once the database is made it can be saved as a file with the write_db command. OpenROAD can then read the database with the read_db command without reading LEF/DEF or Verilog.

The read_lef and read_def commands can be used to build an OpenDB database as shown below. The read_lef -tech flag reads the technology portion of a LEF file. The read_lef -library flag reads the MACROs in the LEF file. If neither of the -tech and -library flags are specified they default to -tech -library if no technology has been read and -library if a technology exists in the database.

.. tabs::

   .. code-tab:: tcl

      read_lef liberty1.lef
      read_def reg1.def
      # Write the db for future runs.
      write_db reg1.db


   .. code-tab:: py

      from openroad import Design, Tech
      tech = Tech()
      tech.readLef("liberty1.lef")
      design = Design(tech)
      design.readDef("reg1.def")

      # Write the db for future runs.
      design.writedb("reg1.db")

The read_verilog command is used to build an OpenDB database as shown below. Multiple Verilog files for a hierarchical design can be read. The link_design command is used to flatten the design and make a database.

.. tabs::

   .. code-tab:: tcl

      read_lef liberty1.lef
      read_verilog reg1.v
      link_design top
      # Write the db for future runs.
      write_db reg1.db


   .. code-tab:: py

      # Not supported in Python

Example scripts

Example scripts demonstrating how to run OpenROAD on sample designs can be found in /test. Flow tests taking sample designs from synthesizable RTL Verilog to detail-routed final layout in the open-source technologies Nangate45 and Sky130HD are shown below.

gcd_nangate45.tcl
aes_nangate45.tcl
tinyRocket_nangate45.tcl
gcd_sky130hd.tcl
aes_sky130hd.tcl
ibex_sky130hd.tcl

Each of these designs use the common script flow.tcl.

Abstract LEF Support

OpenROAD contains an abstract LEF writer that can take your current design and emit an abstract LEF representing the external pins of your design and metal obstructions.

write_abstract_lef (-bloat_factor bloat_factor|-bloat_occupied_layers) \
		   filename

Options

Switch Name	Description
-bloat_factor	Specifies the bloat factor used when bloating then merging shapes into LEF obstructions. The factor is measured in # of default metal pitches for the respective layer. A factor of 0 will result in detailed LEF obstructions
-bloat_occupied_layers	Generates cover obstructions (obstructions over the entire layer) for each layer where shapes are present

Examples

read reg1.db

# Bloat metal shapes by 3 pitches (respectively for every layer) and then merge
write_abstract_lef -bloat_factor 3 reg1_abstract.lef

# Produce cover obstructions for each layer with shapes present
write_abstract_lef -bloat_occupied_layers reg1_abstract.lef

Global Connections

Add global connections

The add_global_connection command is used to specify how to connect power and ground pins on design instances to the appropriate supplies.

add_global_connection -net net_name \
                      [-inst_pattern inst_regular_expression] \
                      -pin_pattern pin_regular_expression \
                      (-power|-ground) \
                      [-region region_name]

Options

Switch Name	Description
-net	Specifies the name of the net in the design to which connections are to be added
-inst_pattern	Optional specifies a regular expression to select a set of instances from the design. (Default: .*)
-pin_pattern	Species a regular expression to select pins on the selected instances to connect to the specified net
-power	Specifies that the net it a power net
-ground	Specifies that the net is a ground net
-region	Specifies the name of the region for this rule

Examples

# Stdcell power/ground pins
add_global_connection -net VDD -pin_pattern {^VDD$} -power
add_global_connection -net VSS -pin_pattern {^VSS$} -ground

# SRAM power ground pins
add_global_connection -net VDD -pin_pattern {^VDDPE$}
add_global_connection -net VDD -pin_pattern {^VDDCE$}
add_global_connection -net VSS -pin_pattern {^VSSE$}

Perform global connections

The global_connect command is used to connect power and ground pins on design instances to the appropriate supplies.

global_connect

Clear global connection rules

The clear_global_connect command is used remove all defined global connection rules.

clear_global_connect

Report global connection rules

The report_global_connect command is used print out the currently defined global connection rules.

report_global_connect

Report cell type usage

The report_cell_usage command is used to print out the usage of cells for each type of cell.

report_cell_usage [-verbose] [module instance]

Options

Switch Name	Description
-verbose	Add information about all leaf instances.
module instance	Report cell usage for a specified module instance.

TCL functions

Get the die and core areas as a list in microns: llx lly urx ury

ord::get_die_area
ord::get_core_area

The place_inst command is used to place an instance. If -cell is given then a new instance may be created as well as placed.

sta::define_cmd_args "place_inst" {-name inst_name \
                                   -orientation orientation
                                   -origin xy_origin \
                                   [-cell library_cell] \
                                   [-status status]}

Options

Switch Name	Description
-name	The name of the instance
-orientaton	The orientation of the instance.
-origin	The x and y coordinates for where the instance is placed.
[-cell]	Required if a new instance is to be created.
[-status]	The placement status of the instance. Default PLACED

FAQs

Check out GitHub discussion about this tool.

License

BSD 3-Clause License.