OpenLane/docs/source/reference/configuration.md

Flow Configuration Variables

This page describes user-configurable flow variables and their default values.

Variables that are defined by the PDK configuration support files and not the
flow itself are listed [in this chapter](./pdk_configuration.md).

Deprecated variables are automatically translated to their new names for at least
6 months. Removed variables will be entirely ignored by the flow.

Load Order

The default configuration files in this folder are loaded in the order described in load_order.txt.

Required variables

Variable	Description
DESIGN_NAME	The name of the top level module of the design
VERILOG_FILES	The path of the design's verilog files, whitespace-delimited.
CLOCK_PERIOD	The clock period for the design in nanoseconds.
CLOCK_NET	The name of the net input to root clock buffer used in Clock Tree Synthesis.
CLOCK_PORT	The name of the design's clock port used in Static Timing Analysis.

Optional variables

These variables are optional that can be specified in the design configuration file.

General

Variable	Description
PDK	Specifies the process design kit (PDK). (Default: sky130A )
STD_CELL_LIBRARY	Specifies the standard cell library to be used under the specified PDK. (Default: sky130_fd_sc_hd )
STD_CELL_LIBRARY_OPT	Specifies the standard cell library to be used during resizer optimizations. (Default: STD_CELL_LIBRARY )
PDK_ROOT	Specifies the folder path of the PDK. It searches for a config.tcl in $::env(PDK_ROOT)/$::env(PDK)/libs.tech/openlane/ directory and at least have one standard cell library config defined in $::env(PDK_ROOT)/$::env(PDK)/libs.tech/openlane/$::env(STD_CELL_LIBRARY).
DIODE_PADDING	Number of sites to left pad DIODE_CELL during detailed placement. (Default: 2 sites)
MERGED_LEF	Points to merged.lef, which is a merger of various LEF files, including the technology lef, cells lef, any custom lefs, and IO lefs.
NO_SYNTH_CELL_LIST	Specifies the file that contains the don't-use-cell-list to be excluded from the liberty file during synthesis. If it's not defined, this path is searched $::env(PDK_ROOT)/$::env(PDK)/libs.tech/openlane/$::env(STD_CELL_LIBRARY)/no_synth.cells and if it's not found, then the original liberty will be used as is.
DRC_EXCLUDE_CELL_LIST	Specifies the file that contains the don't-use-cell-list to be excluded from the liberty file during synthesis and timing optimizations. If it's not defined, this path is searched $::env(PDK_ROOT)/$::env(PDK)/libs.tech/openlane/$::env(STD_CELL_LIBRARY)/drc_exclude.cells and if it's not found, then the original liberty will be used as is. In other words, DRC_EXCLUDE_CELL_LIST contain the only excluded cell list in timing optimizations.

Macros/Chip Integration

Variable	Description
VERILOG_FILES_BLACKBOX	Black-boxed, Verilog files where the implementation is ignored. Useful for pre-hardened macros you incorporate into your design, used during synthesis and opensta. /// sta-blackbox can be added to a file in order skip that file while doing sta. This will blackbox all the modules definied inside that file. It is recommended to provide a gatelevel netlist whenever possible to do full sta.
EXTRA_LEFS	Specifies LEF files of pre-hardened macros used in the current design, used in placement and routing.
EXTRA_LIBS	Specifies LIB files of pre-hardened macros used in the current design, used during timing analysis. (Optional)
EXTRA_GDS_FILES	Specifies GDS files of pre-hardened macros used in the current design, used during tape-out.

Linting

Variable	Description
LINTER_RELATIVE_INCLUDES‡	When a file references an include file, resolve the filename relative to the path of the referencing file, instead of relative to the current directory. (Default: 1)
LINTER_DEFINES	A list of defines that are passed to the linter. The syntax for each item in the list is as follows <define>(=<value>). (=value) is optional. Both PnR=1 or PnR are accepted (Default: SYNTH_DEFINES)
LINTER_INCLUDE_PDK_MODELS	Enables including verilog models of the pdk with the linter. This is useful when the design has hand instantiated macros. This variable has no effect if the PDK/STD_CELL_LIBRARY aren't supported. Currently, sky130A/sky130_fd_sc_hd and sky130B/sky130_fd_sc_hd are the only ones supported (Default: 1)

‡ Variable previously prefixed VERILATOR_ have had their prefix changed to LINTER_. The replaced variable is deprecated and will be translated to its new form automatically by the flow.

Synthesis

Variable	Description
SYNTH_AUTONAME	Add a synthesis step to generate names for instances. This results in instance names that can be very long, but may be more useful than the internal names that are six digit numbers. Enabled = 1, Disabled = 0 (Default: 0)
SYNTH_BIN	The yosys binary used in the flow. (Default: yosys)
SYNTH_CAP_LOAD	The capacitive load on the output ports in femtofarads. (Default: 33.5 ff)
SYNTH_DEFINES	Specifies verilog defines. Variable should be provided as a json/tcl list. (Default: NONE)
SYNTH_MAX_FANOUT	The max load that the output ports can drive. (Default: 10 cells)
SYNTH_MAX_TRAN	The max transition time (slew) from high to low or low to high on cell inputs in ns. If unset, the library's default maximum transition time will be used.
SYNTH_CLOCK_UNCERTAINTY	Specifies a value for the clock uncertainty/jitter for timing analysis. (Default: 0.25)
SYNTH_CLOCK_TRANSITION	Specifies a value for the clock transition /slew for timing analysis. (Default: 0.15)
SYNTH_TIMING_DERATE	Specifies a derating factor to multiply the path delays with. It specifies the upper and lower ranges of timing. (Default: +5%/-5%)
SYNTH_STRATEGY	Strategies for abc logic synthesis and technology mapping Possible values are DELAY/AREA 0-4/0-3; the first part refers to the optimization target of the synthesis strategy (area vs. delay) and the second one is an index. (Default: AREA 0)
SYNTH_BUFFERING	Enables abc cell buffering Enabled = 1, Disabled = 0 (Default: 1)
SYNTH_SIZING	Enables abc cell sizing (instead of buffering) Enabled = 1, Disabled = 0 (Default: 0)
SYNTH_READ_BLACKBOX_LIB	A flag that enable reading the full(untrimmed) liberty file as a blackbox for synthesis. Please note that this is not used in technology mapping. This should only be used when trying to preserve gate instances in the rtl of the design. Enabled = 1, Disabled = 0 (Default: 0)
SYNTH_NO_FLAT	A flag that disables flattening the hierarchy during synthesis, only flattening it after synthesis, mapping and optimizations. Enabled = 1, Disabled = 0 (Default: 0)
SYNTH_SHARE_RESOURCES	A flag that enables yosys to reduce the number of cells by determining shareable resources and merging them. Enabled = 1, Disabled = 0 (Default: 1)
SYNTH_ADDER_TYPE	Adder type to which the $add and $sub operators are mapped to. Possible values are YOSYS/FA/RCA/CSA; where YOSYS refers to using Yosys internal adder definition, FA refers to full-adder structure, RCA refers to ripple carry adder structure, and CSA refers to carry select adder. (Default: YOSYS)
SYNTH_EXTRA_MAPPING_FILE	Points to extra techmap file for yosys that runs right after yosys synth before generic techmap. (Default: "")
SYNTH_PARAMETERS	Whitespace-delimited key value pairs to be chparamed in Yosys. In the format key1=value1 key2=value2 (Default: None)
SYNTH_ELABORATE_ONLY	"Elaborate" the design only without attempting any logic mapping. Useful when dealing with structural Verilog netlists. (Default: 0)
CLOCK_BUFFER_FANOUT	Fanout of clock tree buffers. (Default: 16)
BASE_SDC_FILE	Specifies the base sdc file to source before running Static Timing Analysis. (Default: $::env(OPENLANE_ROOT)/scripts/base.sdc)
VERILOG_INCLUDE_DIRS	Specifies the verilog includes directories. Optional.
SYNTH_FLAT_TOP	Specifies whether or not the top level should be flattened during elaboration. 1 = True, 0= False (Default: 0 )
IO_PCT	Specifies the percentage of the clock period used in the input/output delays. Ranges from 0 to 1.0. (Default: 0.2)
SYNTH_BUFFER_DIRECT_WIRES	Insert buffer cells into the design for directly connected wires. (Default: 1)
SYNTH_SPLITNETS	Splits multi-bit nets into single-bit nets. (Default: 1)
SYNTH_TOP_LEVEL	Deprecated: Use SYNTH_ELABORATE_ONLY: "Elaborate" the design only without attempting any logic mapping. Useful when dealing with structural Verilog netlists.

STA

Variable	Description
STA_REPORT_POWER	Enables reporting power in sta. (Default: 1)
EXTRA_SPEFS	Specifies min, nom, max spef files for modules(s). Variable should be provided as a json/tcl list or a space delimited tcl string. Note that a module name is provided not an instance name. A module may have multiple instances. Each module must have define 3 files, one for each corner. For example: module1 min1 nom1 max1 module2 min2 nom2 max2. A file can be used multiple time in case of absence of other corner files. For example: module nom nom nom. In this case, the nom file will be used in all corners of sta. At all times a module must specify 3 files. (Default: NONE)
STA_WRITE_LIB	Controls whether a timing model is written using OpenROAD OpenSTA after static timing analysis. This is an option as it in its current state, the timing model generation (and the model itself) can be quite buggy. (Default: 1)

Floorplanning

Variable	Description
FP_CORE_UTIL	The core utilization percentage. (Default: 50 percent)
FP_ASPECT_RATIO	The core's aspect ratio (height / width). (Default: 1)
FP_SIZING	Whether to use relative sizing by making use of FP_CORE_UTIL or absolute one using DIE_AREA. (Default: "relative" - accepts "absolute" as well)
DIE_AREA	Specific die area to be used in floorplanning when FP_SIZING is set to absolute. Specified as a 4-corner rectangle "x0 y0 x1 y1". Units in μm (Default: unset)
CORE_AREA	Specific core area (i.e. die area minus margins) to be used in floorplanning when FP_SIZING is set to absolute. Specified as a 4-corner rectangle "x0 y0 x1 y1". Units in μm (Default: unset)
FP_IO_MODE	Decides the mode of the random IO placement option. 0=matching mode, 1=random equidistant mode (Default: 1)
FP_WELLTAP_CELL	The name of the welltap cell during welltap insertion.
FP_ENDCAP_CELL	The name of the endcap cell during endcap insertion.
FP_PDN_CFG	Points to a PDN configuration file that describes how to construct the PDN in detail. (Default: scripts/openroad/common/pdn_cfg.tcl)
FP_PDN_AUTO_ADJUST	Decides whether or not the flow should attempt to re-adjust the power grid, in order for it to fit inside the core area of the design, if needed. 1=enabled, 0 =disabled (Default: 1)
FP_PDN_SKIPTRIM	Enables -skip_trim option during pdngen which skips the metal trim step, which attempts to remove metal stubs 1=enabled, 0 =disabled (Default: 1)
FP_TAPCELL_DIST	The horizontal distance between two tapcell columns (Default: 14)
FP_IO_VEXTEND	Extends the vertical io pins outside of the die by the specified units (Default: 0 Disabled)
FP_IO_HEXTEND	Extends the horizontal io pins outside of the die by the specified units (Default: 0 Disabled)
FP_IO_VLENGTH	The length of the vertical IOs in microns. (Default: 4)
FP_IO_HLENGTH	The length of the horizontal IOs in microns. (Default: 4)
FP_IO_VTHICKNESS_MULT	A multiplier for vertical pin thickness. Base thickness is the pins layer minwidth (Default: 2)
FP_IO_HTHICKNESS_MULT	A multiplier for horizontal pin thickness. Base thickness is the pins layer minwidth (Default: 2)
FP_IO_UNMATCHED_ERROR	Exit on unmatched pins in a provided FP_PIN_ORDER_CFG file. 0=Disable 1=Enable. (Default: 1 Enabled)
BOTTOM_MARGIN_MULT	The core margin, in multiples of site heights, from the bottom boundary. If FP_SIZING is absolute and CORE_AREA is set, this variable has no effect. (Default: 4)
TOP_MARGIN_MULT	The core margin, in multiples of site heights, from the top boundary. If FP_SIZING is absolute and CORE_AREA is set, this variable has no effect. (Default: 4)
LEFT_MARGIN_MULT	The core margin, in multiples of site widths, from the left boundary. If FP_SIZING is absolute and CORE_AREA is set, this variable has no effect. (Default: 12)
RIGHT_MARGIN_MULT	The core margin, in multiples of site widths, from the right boundary. If FP_SIZING is absolute and CORE_AREA is set, this variable has no effect. (Default: 12)
FP_PDN_CORE_RING	Enables adding a core ring around the design. More details on the control variables in the pdk configurations documentation. 0=Disable 1=Enable. (Default: 0)
FP_PDN_ENABLE_GLOBAL_CONNECTIONS	Enables power connection to std cells. It is rare that this variable needs to be disabled (Default: 1)
FP_PDN_ENABLE_RAILS	Enables the creation of rails in the power grid. 0=Disable 1=Enable. (Default: 1)
FP_PDN_ENABLE_MACROS_GRID	Enables the connection of macros to the top level power grid. 0=Disable 1=Enable. (Default: 1)
FP_PDN_MACRO_HOOKS	Specifies explicit power connections of internal macros to the top level power grid. As a comma-delimited (warning) list of macro instance names, power domain vdd and ground net names, and macro vdd and ground pin names: <instance_name> <vdd_net> <gnd_net> <vdd_pin> <gnd_pin>
FP_PDN_CHECK_NODES	Enables checking for unconnected nodes in the power grid. 0=Disable 1=Enable. (Default: 1)
FP_TAP_HORIZONTAL_HALO	Specify the horizontal halo size around macros during tap insertion. The value provided is in microns. (Default: 10)
FP_TAP_VERTICAL_HALO	Specify the vertical halo size around macros during tap insertion. The value provided is in microns. (Default: set to the value of FP_TAP_HORIZONTAL_HALO)
FP_PDN_HORIZONTAL_HALO	Sets the horizontal halo around the macros during power grid insertion. The value provided is in microns. (Default: 10)
FP_PDN_VERTICAL_HALO	Sets the vertical halo around the macros during power grid insertion. The value provided is in microns. (Default: set to the value of FP_PDN_HORIZONTAL_HALO)
DESIGN_IS_CORE	Controls the layers used in the power grid. Depending on whether the design is the core of the chip or a macro inside the core. 1=Is a Core, 0=Is a Macro (Default: 1)
FP_PIN_ORDER_CFG	Points to the pin order configuration file to set the pins in specific directions (S, W, E, N). If not set, then the IO pins will be placed based on one of the other methods depending on the rest of the configurations. $<number> i.e. $1 can be used to place a virtual pin where <number> is the count of virtual pins. This can create separation between pins. You can also use @min_distance=<number> i.e. @min_distance=0.8 to set preferred min distance between pins in a specific direction. See spm configuration file as an example. (Default: NONE)
FP_CONTEXT_DEF	Points to the parent DEF file that includes this macro/design and uses this DEF file to determine the best locations for the pins. It must be used with FP_CONTEXT_LEF, otherwise it's considered non-existing. If not set, then the IO pins will be placed based on one of the other methods depending on the rest of the configurations. (Default: NONE)
FP_CONTEXT_LEF	Points to the parent LEF file that includes this macro/design and uses this LEF file to determine the best locations for the pins. It must be used with FP_CONTEXT_DEF, otherwise it's considered non-existing. If not set, then the IO pins will be placed based on one of the other methods depending on the rest of the configurations. (Default: NONE)
FP_DEF_TEMPLATE	Points to the DEF file to be used as a template when running apply_def_template. This will be used to exctract pin names, locations, shapes -excluding power and ground pins- as well as the die area and replicate all this information in the CURRENT_DEF.
VDD_NETS	Specifies the power nets/pins to be used when creating the power grid for the design.
GND_NETS	Specifies the ground nets/pins to be used when creating the power grid for the design.
SYNTH_USE_PG_PINS_DEFINES	Specifies the power guard used in the verilog source code to specify the power and ground pins. This is used to automatically extract VDD_NETS and GND_NET variables from the verilog, with the assumption that they will be order inout vdd1, inout gnd1, inout vdd2, inout gnd2, ....
FP_IO_MIN_DISTANCE	The minmimum distance between the IOs in microns. (Default: 3)
FP_PADFRAME_CFG	A configuration file passed to padringer, a padframe generator. (Default: NONE)
PDN_CFG	Deprecated: Use FP_PDN_CFG: Points to a PDN configuration file that describes how to construct the PDN in detail.
FP_HORIZONTAL_HALO	Deprecated: Use FP_PDN_HORIZONTAL_HALO: Sets the horizontal halo around the macros during power grid insertion. The value provided is in microns.
FP_PDN_VERTICAL_HALO	Deprecated: Use FP_PDN_VERTICAL_HALO: Sets the vertical halo around the macros during power grid insertion. The value provided is in microns.
FP_PDN_IRDROP	Removed: No point running it this early in the flow: Enable calculation of power grid IR drop during PDN generation.

Deprecated I/O Layer variables

These variables worked initially, but they were too sky130 specific and will be removed. Currently, if you define them in your design, they'll be used, but it's recommended to update your configuration to use FP_IO_HLAYER and FP_IO_VLAYER, which are defined in the PDK.

Variable	Description
FP_IO_HMETAL	The metal layer on which to place the io pins horizontally (top and bottom of the die). (Default: 4)
FP_IO_VMETAL	The metal layer on which to place the io pins vertically (sides of the die) (Default: 3)

Resizer (Common)

Variable	Description
RSZ_LIB	Points to one or more lib files, corresponding to the typical corner, that is used during resizer optimizations. (Default: set to the value of PDK's LIB_SYNTH)
RSZ_LIB_FASTEST	Points to one or more lib files, corresponding to the fastest corner, that is used during resizer optimizations. (Default: set to the value of PDK's LIB_FASTEST)
RSZ_LIB_SLOWEST	Points to one or more lib files, corresponding to the slowest corner, that is used during resizer optimizations. (Default: set to the value of PDK's LIB_SLOWEST)
RSZ_MULTICORNER_LIB	A flag for reading fastest and slowest corner during resizer optimizations. (Default: 1)
RSZ_DONT_TOUCH_RX	A single regular expression designating nets as "don't touch" by resizer optimizations. (Default: $^ (matches nothing))
RSZ_DONT_TOUCH	A list of nets or instances to set as "don't touch". (Default: Empty)
LIB_RESIZER_OPT	Deprecated: Use RSZ_LIB: Points to the lib file, corresponding to the typical corner, that is used during resizer optimizations. This is copy of LIB_SYNTH.

Placement

Variable	Description
PL_TARGET_DENSITY	The desired placement density of cells. It reflects how spread the cells would be on the core area. 1 = closely dense. 0 = widely spread (Default: ($::env(FP_CORE_UTIL) + 10 + (5 * $::env(GPL_CELL_PADDING)) ) / 100.0)
PL_TIME_DRIVEN	Specifies whether the placer should use time driven placement. 0 = false, 1 = true (Default: 1)
PL_BASIC_PLACEMENT	Specifies whether the placer should run basic placement. Basic placement is used for extremely simple, low-density designs of only a few dozens of gates, and should be disabled for most designs. 0 = false, 1 = true (Default: 0)
PL_SKIP_INITIAL_PLACEMENT	Specifies whether the placer should run initial placement or not. 0 = false, 1 = true (Default: 0)
PL_RANDOM_GLB_PLACEMENT	Specifies whether the placer should run random placement or not. This is useful if the design is tiny (less than 100 cells). 0 = false, 1 = true (Default: 0)
PL_RANDOM_INITIAL_PLACEMENT	Specifies whether the placer should run random placement or not followed by replace's initial placement. This is useful if the design is tiny (less than 100 cells). 0 = false, 1 = true (Default: 0)
PL_ROUTABILITY_DRIVEN	Specifies whether the placer should use routability driven placement. 0 = false, 1 = true (Default: 1)
PL_RESIZER_TIE_SEPERATION	Distance between load and an inserted tie cell in microns. (Default: 0)
PL_RESIZER_DESIGN_OPTIMIZATIONS	Specifies whether resizer design optimizations should be performed or not. 0 = false, 1 = true (Default: 1)
PL_RESIZER_TIMING_OPTIMIZATIONS	Specifies whether resizer timing optimizations should be performed or not. 0 = false, 1 = true (Default: 1)
PL_RESIZER_MAX_WIRE_LENGTH	Specifies the maximum wire length cap used by resizer to insert buffers. If set to 0, no buffers will be inserted. Value in microns. (Default: 0)
PL_RESIZER_MAX_SLEW_MARGIN	Specifies a margin for the slews in percentage. (Default: 20)
PL_RESIZER_MAX_CAP_MARGIN	Specifies a margin for the capacitances in percentage. (Default: 20)
PL_RESIZER_HOLD_SLACK_MARGIN	Specifies a time margin for the slack when fixing hold violations. Normally the resizer will stop when it reaches zero slack. This option allows you to overfix. (Default: 0.1ns.)
PL_RESIZER_SETUP_SLACK_MARGIN	Specifies a time margin for the slack when fixing setup violations. (Default: 0.05ns)
PL_RESIZER_HOLD_MAX_BUFFER_PERCENT	Specifies a max number of buffers to insert to fix hold violations. This number is calculated as a percentage of the number of instances in the design. (Default: 50)
PL_RESIZER_SETUP_MAX_BUFFER_PERCENT	Specifies a max number of buffers to insert to fix setup violations. This number is calculated as a percentage of the number of instances in the design. (Default: 50)
PL_RESIZER_ALLOW_SETUP_VIOS	Allows setup violations when fixing hold. (Default: 0)
PL_WIRELENGTH_COEF	Global placement initial wirelength coefficient. Decreasing the variable will modify the initial placement of the standard cells to reduce the wirelengths. (Default: 0.25).
DONT_USE_CELLS	The list of cells to not use during resizer optimizations. (Default: the contents of DRC_EXCLUDE_CELL_LIST)
PL_ESTIMATE_PARASITICS	Specifies whether or not to run STA after global placement using OpenROAD's estimate_parasitics -placement and generates reports under logs/placement. 1 = Enabled, 0 = Disabled. (Default: 1)
PL_OPTIMIZE_MIRRORING	Specifies whether or not to run an optimize_mirroring pass whenever detailed placement happens. This pass will mirror the cells whenever possible to optimize the design. 1 = Enabled, 0 = Disabled. (Default: 1)
PL_RESIZER_BUFFER_INPUT_PORTS	Specifies whether or not to insert buffers on input ports whenever resizer optimizations are run. For this to be used, PL_RESIZER_DESIGN_OPTIMIZATIONS must be set to 1. 1 = Enabled, 0 = Disabled. (Default: 1)
PL_RESIZER_BUFFER_OUTPUT_PORTS	Specifies whether or not to insert buffers on output ports whenever resizer optimizations are run. For this to be used, PL_RESIZER_DESIGN_OPTIMIZATIONS must be set to 1. 1 = Enabled, 0 = Disabled. (Default: 1)
PL_RESIZER_REPAIR_TIE_FANOUT	Specifies whether or not to repair tie cells fanout whenever resizer optimizations are run. For this to be used, PL_RESIZER_DESIGN_OPTIMIZATIONS must be set to 1. 1 = Enabled, 0 = Disabled. (Default: 1)
PL_MAX_DISPLACEMENT_X	Specifies how far an instance can be moved along the X-axis when finding a site where it can be placed during detailed placement. (Default: 500μm)
PL_MAX_DISPLACEMENT_Y	Specifies how far an instance can be moved along the Y-axis when finding a site where it can be placed during detailed placement. (Default: 100μm)
PL_MACRO_HALO	Macro placement halo. Format: {Horizontal} {Vertical} (Default: 0 0μm).
PL_MACRO_CHANNEL	Channel widths between macros. Format: {Horizontal} {Vertical} (Default: 0 0μm).
MACRO_PLACEMENT_CFG	Specifies the path a file specifying how openlane should place certain macros
UNBUFFER_NETS	Deprecated: Use RSZ_DONT_TOUCH_RX: A regular expression used to match nets from which to remove buffers after every resizer run. Useful for analog ports in mixed-signal designs where OpenROAD may sometimes add a buffer.
DONT_BUFFER_PORTS	Removed: Use RSZ_DONT_TOUCH_RX: Semicolon;delimited list of nets from which to remove buffers.

CTS

Variable	Description
RUN_CTS	Enable clock tree synthesis. (Default: 1)
CTS_TOLERANCE	An integer value that represents a tradeoff of QoR and runtime. Higher values will produce smaller runtime but worse QoR (Default: 100)
CTS_SINK_CLUSTERING_SIZE	Specifies the maximum number of sinks per cluster. (Default: 25)
CTS_SINK_CLUSTERING_MAX_DIAMETER	Specifies maximum diameter (in micron) of sink cluster. (Default: 50)
CTS_REPORT_TIMING	Specifies whether or not to run STA after clock tree synthesis using OpenROAD's estimate_parasitics -placement and generates reports under logs/cts. 1 = Enabled, 0 = Disabled. (Default: 1)
CTS_CLK_MAX_WIRE_LENGTH	Specifies the maximum wire length on the clock net. Value in microns. (Default: 0)
CTS_DISABLE_POST_PROCESSING	Specifies whether or not to disable post cts processing for outlier sinks. (Default: 0)
CTS_DISTANCE_BETWEEN_BUFFERS	Specifies the distance (in microns) between buffers when creating the clock tree (Default: 0)
LIB_CTS	The liberty file used for CTS for typical corner. By default, this is the LIB_SYNTH minus the cells with drc errors as specified by the drc exclude list. (Default: $::env(cts_tmpfiles)/cts.lib)
LIB_CTS_SLOWEST	The liberty file used for CTS for slowest corner. By default, this is the LIB_SLOWEST minus the cells with drc errors as specified by the drc exclude list. (Default: $::env(cts_tmpfiles)/cts-slowest.lib)
LIB_CTS_FASTEST	The liberty file used for CTS for fastest corner. By default, this is the LIB_FASTEST minus the cells with drc errors as specified by the drc exclude list. (Default: $::env(cts_tmpfiles)/cts-fastest.lib)
CTS_MULTICORNER_LIB	A flag for reading fastest and slowest corner during CTS. (Default: 1)
CLOCK_TREE_SYNTH	Deprecated: Use RUN_CTS: Enable clock tree synthesis. 1 = Enabled, 0 = Disabled.
FILL_INSERTION	Removed: Use RUN_FILL_INSERTION: Enables fill cells insertion after CTS. 1 = Enabled, 0 = Disabled.
RUN_SIMPLE_CTS	Removed: TritonCTS is always run: Run an alternative simple clock tree synthesis after synthesis instead of TritonCTS. 1 = Enabled, 0 = Disabled.
CTS_TARGET_SKEW	Removed: No longer supported by underlying utility. The target clock skew in picoseconds. (Default: 200ps)

Routing

Variable	Description
GLOBAL_ROUTER	Specifies which global router to use. Values: fastroute. (cugr is deprecated and fastroute will be used instead.) (Default: fastroute)
DETAILED_ROUTER	Specifies which detailed router to use. Values: tritonroute. (drcu/tritonroute_or are both deprecated and tritonroute will be used instead.) (Default: tritonroute)
ROUTING_CORES	Specifies the number of threads to be used in TritonRoute. Can be overriden via environment variable. (Default: 2)
RT_CLOCK_MIN_LAYER	The name of lowest layer to be used in routing the clock net. (Default: RT_MIN_LAYER)
RT_CLOCK_MAX_LAYER	The name of highest layer to be used in routing the clock net. (Default: RT_MAX_LAYER)
GLB_RESIZER_TIMING_OPTIMIZATIONS	Specifies whether resizer timing optimizations should be performed after global routing or not. 1 = Enabled, 0 = Disabled. (Default: 1)
GLB_RESIZER_DESIGN_OPTIMIZATIONS	Specifies whether resizer design optimizations should be performed after global routing or not. 1 = Enabled, 0 = Disabled. (Default: 1)
GLB_RESIZER_MAX_WIRE_LENGTH	Specifies the maximum wire length cap used by resizer to insert buffers. If set to 0, no buffers will be inserted. Value in microns. (Default: 0)
GLB_RESIZER_MAX_SLEW_MARGIN	Specifies a margin for the slews. (Default: 10)
GLB_RESIZER_MAX_CAP_MARGIN	Specifies a margin for the capacitances. (Default: 10)
GLB_RESIZER_HOLD_SLACK_MARGIN	Specifies a time margin for the slack when fixing hold violations. Normally the resizer will stop when it reaches zero slack. This option allows you to overfix. (Default: 0.05ns)
GLB_RESIZER_SETUP_SLACK_MARGIN	Specifies a time margin for the slack when fixing setup violations. (Default: 0.025ns)
GLB_RESIZER_HOLD_MAX_BUFFER_PERCENT	Specifies a max number of buffers to insert to fix hold violations. This number is calculated as a percentage of the number of instances in the design. (Default: 50)
GLB_RESIZER_SETUP_MAX_BUFFER_PERCENT	Specifies a max number of buffers to insert to fix setup violations. This number is calculated as a percentage of the number of instances in the design. (Default: 50)
GLB_RESIZER_ALLOW_SETUP_VIOS	Allows setup violations when fixing hold. (Default: 0)
GLB_OPTIMIZE_MIRRORING	Specifies whether or not to run an optimize_mirroring pass whenever detailed placement happens after Routing timing optimization. This pass will mirror the cells whenever possible to optimize the design. 1 = Enabled, 0 = Disabled. (Default: 1)
GRT_ALLOW_CONGESTION‡	Allow congestion in the resulting guides. 0 = false, 1 = true (Default: 0)
GRT_OVERFLOW_ITERS‡	The maximum number of iterations waiting for the overflow to reach the desired value. (Default: 50)
GRT_ANT_ITERS‡	The maximum number of iterations for global router repair_antenna. This option is only available when GRT_REPAIR_ANTENNAS is enabled. (Default: 15)
GRT_ANT_MARGIN‡	The margin to over fix antenna violations in global routing as a percentage. This option is only available when GRT_REPAIR_ANTENNAS is enabled. (Default: 10)
GRT_ESTIMATE_PARASITICS‡	Specifies whether or not to run STA after global routing using OpenROAD's estimate_parasitics -global_routing and generates reports under logs/routing. 1 = Enabled, 0 = Disabled. (Default: 1)
GRT_MAX_DIODE_INS_ITERS‡	Controls the maximum number of iterations at which re-running Fastroute for diode insertion stops. Each iteration ARC detects the violations and FastRoute fixes them by inserting diodes, then producing the new DEF. The number of antenna violations is compared with the previous iteration and if they are equal or the number is greater the iterations stop and the DEF from the previous iteration is used in the rest of the flow. If the current antenna violations reach zero, the current def will be used and the iterations will not continue. This option is only available in when GRT_REPAIR_ANTENNAS is enabled. (Default: 1)
GRT_REPAIR_ANTENNAS‡	Enables OpenROAD's antenna avoidance flow. (Default: 1)
GRT_OBS‡	Specifies custom obstruction to be added prior to global routing. Comma-delimited (warning) list of layer and coordinates: layer llx lly urx ury, where ll and ur stand for "lower left" and "upper right" respectively. (Example: li1 0 100 1000 300, met5 0 0 1000 500) (Default: unset)
GRT_ADJUSTMENT‡	Reduction in the routing capacity of the edges between the cells in the global routing graph. Values range from 0 to 1. 1 = most reduction, 0 = least reduction (Default: 0.3)
GRT_MACRO_EXTENSION‡	Sets the number of GCells added to the blockages boundaries from macros. A GCell is typically defined in terms of Mx routing tracks. The default GCell size is 15 M3 pitches. (Default: 0)
DRT_MIN_LAYER	An optional override to the lowest layer used in detailed routing. For example, in sky130, you may want global routing to avoid li1, but let detailed routing use li1 if it has to. (Default: RT_MIN_LAYER)
DRT_MAX_LAYER	An optional override to the highest layer used in detailed routing. (Default: RT_MAX_LAYER)
DRT_OPT_ITERS	Specifies the maximum number of optimization iterations during Detailed Routing in TritonRoute. (Default: 64)
ROUTING_OPT_ITERS	Removed: Use DRT_OPT_ITERS: Specifies the maximum number of optimization iterations during Detailed Routing in TritonRoute.
GLB_RT_MINLAYER	Removed: Use RT_MIN_LAYER: The number of lowest layer to be used in routing.
GLB_RT_MAXLAYER	Removed: Use RT_MAX_LAYER: The number of highest layer to be used in routing.
GLB_RT_CLOCK_MINLAYER	Removed: Use RT_CLOCK_MIN_LAYER: The number of lowest layer to be used in routing the clock net.
GLB_RT_CLOCK_MAXLAYER	Removed: Use RT_CLOCK_MIN_LAYER: The number of highest layer to be used in routing the clock net.
GLB_RT_L{1/2/3/4/5/6}_ADJUSTMENT	Removed: See PDK variable GRT_LAYER_ADJUSTMENTS instead: Reduction in the routing capacity of the edges between the cells in the global routing graph but specific to a metal layer in sky130A. Values ranged from 0 to 1
GLB_RT_UNIDIRECTIONAL	Removed: Allow unidirectional routing. 1 = Enabled, 0 = Disabled.
GLB_RT_TILES	Removed: The size of the GCELL used by Fastroute during global routing.

‡ Variable previously prefixed GLB_RT_ have had its prefix changed to GRT_. The replaced variable is deprecated and will be translated to its new form automatically by the flow.

RC Extraction

Variable	Description
SPEF_EXTRACTOR	Specifies which spef extractor to use. Values: openrcx or (removed: def2spef). (Default: openrcx)
RCX_MERGE_VIA_WIRE_RES	Specifies whether to merge the via resistance with the wire resistance or separate it from the wire resistance. 1 = Merge via resistance, 0 = Separate via resistance (Default: 1)
RCX_SDC_FILE	Specifies SDC file to be used for RCX-based STA, which can be different from the one used for implementation. (Default: BASE_SDC_FILE)
SPEF_WIRE_MODEL	Removed: Specifies the wire model used in SPEF extraction. Options are L or Pi
SPEF_EDGE_CAP_FACTOR	Removed: Specifies the edge capacitance factor used in SPEF extraction. Ranges from 0 to 1

IR Drop Analysis

Variable	Description
VSRC_LOC_FILES	PSM loc file for power and ground nets. Variable should be provided as a json/tcl list or a space delimited tcl string as follows: net1 file1 net2 file2. See this for more info. (Default: NONE)

Magic

Variable	Description
MAGIC_PAD	A flag to pad the views generated by magic (.mag, .lef, .gds) with one site. 1 = Enabled, 0 = Disabled (Default: 0 )
MAGIC_ZEROIZE_ORIGIN	A flag to move the layout such that it's origin in the lef generated by magic is 0,0. 1 = Enabled, 0 = Disabled (Default: 1 )
MAGIC_GENERATE_GDS	A flag to generate gds view via magic. 1 = Enabled, 0 = Disabled (Default: 1 )
MAGIC_GENERATE_LEF	A flag to generate lef view via magic. 1 = Enabled, 0 = Disabled (Default: 1 )
MAGIC_GENERATE_MAGLEF	A flag to generate maglef view via magic. Requires MAGIC_GENERATE_LEF to be also set. 1 = Enabled, 0 = Disabled (Default: 1 )
MAGIC_WRITE_FULL_LEF	A flag to specify whether or not the output LEF should include all shapes inside the macro or an abstracted view of the macro lef view via magic. 1 = Full View, 0 = Abstracted View (Default: 0 )
MAGIC_DRC_USE_GDS	A flag to choose whether to run the magic DRC checks on GDS or not. If not, then the checks will be done on the DEF/LEF. 1 = GDS, 0 = DEF/LEF (Default: 1 )
MAGIC_EXT_USE_GDS	A flag to choose whether to run the magic extractions on GDS or DEF/LEF. If GDS was used Device Level LVS will be run. Otherwise, blackbox LVS will be run. 1 = GDS, 0 = DEF/LEF (Default: 0 )
MAGIC_LEF_WRITE_USE_GDS	A flag to choose whether to run the magic lef write on GDS or DEF/LEF. 1 = GDS, 0 = DEF/LEF (Default: 0 )
MAGIC_INCLUDE_GDS_POINTERS	A flag to choose whether to include GDS pointers in the generated mag files or not. 1 = Enabled, 0 = Disabled (Default: 0 )
MAGIC_DISABLE_HIER_GDS	A flag to disable cif hier and array during GDSII writing.* 1=Enabled <so this hier gds will be disabled>, 0=Disabled <so this hier gds will be enabled>. (Default: 1 )
MAGIC_DEF_NO_BLOCKAGES	A flag to choose whether blockages are read with DEF files or not (they are read as a sheet of metal by Magic). 1 = No Blockages, 0 = Blockages as Metal Sheets (Default: 1 )
MAGIC_DEF_LABELS	A flag to choose whether labels are read with DEF files or not. From magic docs: "The '-labels' option to the 'def read' command causes each net in the NETS and SPECIALNETS sections of the DEF file to be annotated with a label having the net name as the label text." 1 = Labels, 0 = Unlabeled (Default: 1 )
MAGIC_GDS_ALLOW_ABSTRACT	A flag to allow abstract view of macros during magic gds generation. 1 = Allow, 0 = Disallow (Default: 0 )
MAGIC_GDS_POLYGON_SUBCELLS	A flag to enable polygon subcells in magic for gds read potentially speeding up magic. From magic docs: "Put non-Manhattan polygons. This prevents interations with other polygons on the same plane and so reduces tile splitting" 1 = Allow, 0 = Disallow (Default: 0 )

• Tim Edwards's Explanation on disabling hier gds: The following is an explanation by Tim Edwards, provided in a slack thread, on how this affects the GDS writing process: "Magic can take a very long time writing out GDS while checking hierarchical interactions in a standard cell layout. If your design is all digital, I recommend using "gds *hier write disable" before "gds write" so that it does not try to resolve hierarchical interactions (since by definition, standard cells are designed to just sit next to each other without creating DRC issues). That can actually make the difference between a 20 hour GDS write and a 2 minute GDS write. For a standard cell design that takes up the majority of the user space, a > 24 hour write time (without disabling the hierarchy checks) would not surprise me."

LVS

Variable	Description
LVS_INSERT_POWER_PINS	Enables power pins insertion before running lvs. 1 = Enabled, 0 = Disabled (Default: 1)
LVS_CONNECT_BY_LABEL	Enables connections by label in LVS by skipping extract unique in magic extractions. (Default: 0)
YOSYS_REWRITE_VERILOG	Enables yosys to rewrite the verilog before LVS producing a canonical verilog netlist with verbose wire declarations. 1 = Enabled, 0 = Disabled (Default: 0 )

Flow control

Note: The commands prefixed RUN_ enable or disable a certain step as part of the larger OpenLane flow, not when calling the relevant function standalone. For example, if RUN_DRT is set 0, but calling detailed_routing in interactive mode will still run detailed routing.

Variable	Description
RUN_DRT	Enables detailed routing. 1 = Enabled, 0 = Disabled (Default: 1)
RUN_LVS	Enables running LVS. 1 = Enabled, 0 = Disabled (Default: 1)
RUN_HEURISTIC_DIODE_INSERTION	Runs a script by Sylvain Munaut that inserts diodes heuristically based on . 1 = Enabled, 0 = Disabled (Default: 0)
RUN_MAGIC	Enables running magic and GDSII streaming. 1 = Enabled, 0 = Disabled (Default: 1)
RUN_MAGIC_DRC	Enables running magic DRC on GDSII produced by magic. 1 = Enabled, 0 = Disabled (Default: 1)
RUN_KLAYOUT	Enables running KLayout and GDSII streaming. 1 = Enabled, 0 = Disabled (Default: 1)
RUN_KLAYOUT_DRC	Enables running KLayout DRC on GDSII produced by magic. 1 = Enabled, 0 = Disabled (Default: 0)
RUN_KLAYOUT_XOR	Enables running KLayout XOR on 2 GDSIIs, the defaults are the one produced by magic vs the one produced by klayout. 1 = Enabled, 0 = Disabled (Default: 1)
RUN_SPEF_EXTRACTION	Specifies whether or not to run SPEF extraction on the routed DEF. 1=enabled 0=disabled (Default: 1)
RUN_CVC	Runs CVC on the output spice, which is a Circuit Validity Checker. Voltage aware ERC checker for CDL netlists. 1 = Enabled, 0 = Disabled. (Default: 1)
RUN_IRDROP_REPORT	Creates an IR Drop report using OpenROAD PSM. 1 = Enabled, 0 = Disabled. (Default: 0)
RUN_TAP_DECAP_INSERTION	Enables tap and decap cells insertion after floorplanning. 1 = Enabled, 0 = Disabled (Default: 1)
RUN_FILL_INSERTION	Enables fill cells insertion after cts (if enabled). 1 = Enabled, 0 = Disabled (Default: 1)
KLAYOUT_DRC_KLAYOUT_GDS	Enables running KLayout DRC on GDSII produced by KLayout. 1 = Enabled, 0 = Disabled (Default: 0)
GENERATE_FINAL_SUMMARY_REPORT	Specifies whether or not to generate a final summary report after the run is completed. Check command generate_final_summary_report. 1 = Enabled, 0 = Disabled. (Default: 1)
LEC_ENABLE	Enables logic verification using yosys, for comparing each netlist at each stage of the flow with the previous netlist and verifying that they are logically equivalent. Warning: this will increase the runtime significantly. 1 = Enabled, 0 = Disabled (Default: 0)
USE_GPIO_PADS	Decides whether or not to use the gpio pads in routing by merging their LEF file set in ::env(USE_GPIO_ROUTING_LEF) and blackboxing their verilog modules set in ::env(GPIO_PADS_VERILOG). 1 = Enabled, 0 = Disabled. (Default: 0)
PRIMARY_SIGNOFF_TOOL	Determines whether magic or klayout is the primary signoff tool. (Default: magic)
KLAYOUT_XOR_GDS	If RUN_KLAYOUT_XOR is enabled, this will enable producing a GDS output from the XOR along with it's PNG export. 1 = Enabled, 0 = Disabled (Default: 1)
KLAYOUT_XOR_XML	If RUN_KLAYOUT_XOR is enabled, this will enable producing an XML output from the XOR. 1 = Enabled, 0 = Disabled (Default: 1)
TAKE_LAYOUT_SCROT	Enables running KLayout to take a PNG screenshot of the produced layout (currently configured to run on the results of each stage).1 = Enabled, 0 = Disabled (Default: 0)
KLAYOUT_XOR_THREADS	Specifies number of threads used in klayout xor check (Default: 1)
DIODE_ON_PORTS	Insert diodes on ports with the specified polarities. Available options are none, in, out and both. (Default: none)
HEURISTIC_ANTENNA_THRESHOLD	Minimum manhattan distance of a net to insert a diode in microns. Only applicable for RUN_HEURISTIC_DIODE_INSERTION is enabled. (Default: 90)
USE_ARC_ANTENNA_CHECK	Specifies whether to use the openroad ARC antenna checker or magic antenna checker. 0=magic antenna checker, 1=ARC OR antenna checker (Default: 1)
RUN_LINTER	Enable linter (currently Verilator) (Default: 1)
TAP_DECAP_INSERTION	Deprecated: Use RUN_TAP_DECAP_INSERTION: Enables tap and decap cells insertion after floorplanning. 1 = Enabled, 0 = Disabled.
RUN_ROUTING_DETAILED	Deprecated: Use RUN_DRT: Enables detailed routing. 1 = Enabled, 0 = Disabled. (Default: 1)
DIODE_INSERTION_STRATEGY	Deprecated: Update replacement variables GRT_REPAIR_ANTENNAS and RUN_HEURISTIC_DIODE_INSERTION as per the instructions below: Specifies the insertion strategy of diodes to be used in the flow.
	0: No diode insertion. Equivalent to replacement variables being set to 0.
	1: Removed: Spray diodes.
	2: Removed: Insert fake diodes and replace them with real diodes if needed.
	3: Use OpenROAD's Antenna Avoidance flow. Equivalent to replacement variables being set to 1 and 0 respectively.
	4: Use Sylvain Minaut's custom script for diode insertion. Equivalent to replacement variables being set to 0 and 1 respectively.
	5: Removed: A combination of strategies 2 and 4.
	6: A combination of strategies 3 and 4. Equivalent to replacement variables being set to 1.
MAGIC_CONVERT_DRC_TO_RDB	Removed: Will always run: Specifies whether or not generate a Calibre RDB out of the magic.drc report. Result is saved in <run_path>/results/magic/. 1 = Enabled, 0 = Disabled.
TEST_MISMATCHES	Removed: See ./flow.tcl -test_mismatches: Test for mismatches between the OpenLane tool versions and the current environment. all tests all mismatches. tools tests all except the PDK. pdk only tests the PDK. none disables the check.
QUIT_ON_MISMATCHES	Removed: See ./flow.tcl -ignore_mismatches: Whether to halt the flow execution or not if TEST_MISMATCHES is enabled and any mismatches are found.
KLAYOUT_XOR_GDS	Removed: XML always generated: If RUN_KLAYOUT_XOR is enabled, this will enable producing a GDS output from the XOR along with it's PNG export. 1 = Enabled, 0 = Disabled.
KLAYOUT_XOR_XML	Removed: XML always generated: If RUN_KLAYOUT_XOR is enabled, this will enable producing an XML output from the XOR. 1 = Enabled, 0 = Disabled.

Checkers

Variable	Description
QUIT_ON_SYNTH_CHECKS	Quit if any of the following conditions are met: (1) check -assert in yosys. This checks for combinational loops, conflicting drivers and wires with no drivers. (2) Using a signal that doesn't match a module port size in the RTL. For instance, given such a module module example(x); input x; endmodule it gets instantiated like that example y(2'b11); (3) Found Latches in the design. (4) Out of bound(range) errors in the RTL. e.g. wire [10:0] x; assign x[13] = 1'b1. 1 = Enabled, 0 = Disabled (Default: 1)
SYNTH_CHECKS_ALLOW_TRISTATE	Allow tristate logic in QUIT_ON_SYNTH_CHECKS. 1 = Enabled, 0 = Disabled (Default: 1)
QUIT_ON_UNMAPPED_CELLS	Checks if there are unmapped cells after synthesis and aborts if any was found. 1 = Enabled, 0 = Disabled (Default: 1)
QUIT_ON_ASSIGN_STATEMENTS	Checks for assign statement in the generated gate level netlist and aborts of any was found.1 = Enabled, 0 = Disabled (Default: 0)
QUIT_ON_TR_DRC	Checks for DRC violations after routing and exits the flow if any was found. 1 = Enabled, 0 = Disabled (Default: 1)
QUIT_ON_LONG_WIRE	Exits the flow if any wire length exceeds the threshold set in the PDK. 1 = Enabled, 0 = Disabled (Default: 0)
QUIT_ON_MAGIC_DRC	Checks for DRC violations after magic DRC is executed and exits the flow if any was found. 1 = Enabled, 0 = Disabled (Default: 1)
QUIT_ON_ILLEGAL_OVERLAPS	Checks for illegal overlaps during magic extraction. In some cases, these imply existing undetected shorts in the design. It also exits the flow if any was found. 1 = Enabled, 0 = Disabled (Default: 1)
QUIT_ON_LVS_ERROR	Checks for LVS errors after netgen LVS is executed and exits the flow if any was found. 1 = Enabled, 0 = Disabled (Default: 1)
QUIT_ON_HOLD_VIOLATIONS	Exits the flow on hold violations at the typical corner (Default: 1)
QUIT_ON_SETUP_VIOLATIONS	Exits the flow on setup violations at the typical corner (Default: 1)
QUIT_ON_TIMING_VIOLATIONS	Controls QUIT_ON_HOLD_VIOLATIONS and QUIT_ON_SETUP_VIOLATIONS (Default: 1)
QUIT_ON_LINTER_WARNINGS	Quit on warnings generated by linter (currently Verilator) (Default: 0)
QUIT_ON_LINTER_ERRORS	Quit on errors generated by linter (currently Verilator) (Default: 1)
QUIT_ON_XOR_ERROR	Quit on XOR differences between GDSII generated by Magic and KLayout (Default: 1)

On comma-delimited variables

:::{warning} Comma-delimited variables such as FP_PDN_MACRO_HOOK and GRT_OBS must be expressed in a pretty unorthodox way in JSON for now, either:

    "FP_PDN_MACRO_HOOKS": "first item, second item, third item"

or:

    "FP_PDN_MACRO_HOOKS": [
        "first item,",
        "second item,",
        "third item"
    ]

You'll notice that even as an array, all items except for the last item must include a comma in the string itself.

This is an unfortunate limitation with how Tcl handles arrays, i.e., they're just whitespace-delimited strings. :::