sky130/README - third_party/opencircuitdesign.com/open_pdks - Git at Google

 ------------------------------------
 open_pdks
 ----------------------------------------
 Master PDK generator for SkyWater Sky130
 Hybrid 180nm / 130nm foundry process
 for open source EDA tools
 ----------------------------------------

 -------------------------------------------------------------------------------
 Quick summary (TL;DR):

     Prerequisites:

     	sudo apt install python3

     The Magic VLSI layout tool is used often by the installation.  If you do
     not have it, then obtain it and install with the following:

     	sudo apt install m4 tcsh tcl-dev tk-dev

 	git clone https://github.com/RTimothyEdwards/magic
 	cd magic
 	./configure
 	make
 	sudo make install

     Open_PDKs SKY130 Installation: Most people will want to run the following
     for PDK installation:

 	./configure --enable-sky130-pdk
 	make
 	sudo make install
 	make distclean

     This will download and install the SkyWater SKY130 PDK, the SKY130 setup
     files for xschem, a third-party library containing alphanumeric layouts,
     and others.

     With the above configuration line, the PDK files will be installed into
     the path
 		/usr/local/share/pdk/sky130A/

     From open_pdks version 1.0.269, there is a process variant

 		/usr/local/share/pdk/sky130B/

     which reflects support for ReRAM.

 -------------------------------------------------------------------------------
 Detailed instructions for the patient reader:
 -------------------------------------------------------------------------------
 Prerequisites:

 1. EDA tools:

     For installing files to use with the Magic layout tool, Magic must be installed.
     Obtain Magic from:

 	https://github.com/RTimothyEdwards/magic

     No other tools are required for installation, although open_pdks will
     generate and install the setup files for a number of tools.

 2. Foundry source files [optional]:

     If you do not have the foundry source files, the latest versions of
     each library will be downloaded from github, and installed locally into
     the open_pdks/sources/ directory.  If you have the foundry source files,
     then you can pass the location of each library repository to the
     open_pdks configure script.  The instructions below are needed ONLY
     if you intend to download and install the PDK sources outside of
     open_pdks.  Instructions below are only valid for the SkyWater SKY130
     process.  For other open-source PDKs, instructions can be found in the
     corresponding README file in that PDK directory.

     Obtain sources for the SkyWater sky130 130nm process from the git repository
     at the following location:

 	 https://github.com/efabless/

     As of open_pdks version 1.0.428, the Sky130 sources are no longer under
     a single umbrella repository, so each core library must be downloaded
     individually.  The individual core repositories are:

 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_pr
 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_io
 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_hd
 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_hdll
 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_lp
 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_hs
 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_ms
 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_ls
 	 https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_hvl

     This repositories may go in any convenient location.  To keep the overhead
     low, you may install only the repositories that you need.  At a minimum, the
     I/O library, primitive devices, and the high density and high voltage
     digital standard cell libraries should be installed.  The remaining standard
     cell libraries are optional, as needed for low-leakage, high speed, low power,
     etc., applications.

     Then follow the instructions below for generating the additional files
     for supporting the open source EDA tool flows.

 PDK Installation:

 Step 1:

     Run "configure" to set the paths to the Google/SkyWater source
     repositories and to set the path to the install location.  Note that
     the configure script is located in the open_pdks top level directory,
     not in the foundry subdirctory, and should be run from the top level
     directory.  The primary configure options are as follows:

 	--enable-sky130-pdk
 		This is mandatory for specifying that the installation
 		is for the SKY130 PDK.

 	--with-sky130-variants=all|A|B
 		When set to "all" (which is the default), both variants
 		sky130A and sky130B are generated and installed.   If
 		only one PDK variant needs to be installed, then use
 		this option to restrict the installation to a single
 		PDK variant.

 	--with-sky130-link-targets=none|source
 		"none" copies files from the source directories to
 		the target.  "source" makes symbolic links to the source
 		directories.  Use "source" only if doing a local install,
 		and the source foundry data will not be deleted.  For
 		distribution installations, the value must be set to
 		"none".

 	--with-ef-style
 		This option should not be used except in the context
 		of the Efabless "open galaxy" platform where it is
 		used.  The default is "no".  There are some differences
 		in these two styles, the most important of which being
 		that the order of directories for the IP libraries
 		is <file_format>/<library_name> instead of
 		<library_name>/<file_format>. Other differences
 		include version tracking of the Magic setup files
 		and the location of the technology LEF file.

 	--enable-primitive-sky130[=<path>]
 		The path to the sky130_fd_pr library, a core PDK
 		library containing the primitive device models and
 		layouts.  If the configuration option or the path is
 		not specified, then the library will be downloaded from
 		github automatically.  To disable this package, use
 		"--disable-primitive-sky130".

 	--enable-io-sky130[=<path>]
 		The path to the sky130_fd_io library, a core PDK
 		library containing the padframe cell layouts and data.
 		If the configuration option or the path is not specified,
 		then the library will be downloaded from github
 		automatically.  To disable this package, use
 		"--disable-io-sky130".

 	--enable-sc-hs-sky130[=<path>]
 		The path to the sky130_fd_sc_hs library, a core PDK
 		library containing the high-speed standard cell layouts
 		and data.  If the configuration option or the path is
 		not specified, then the library will be downloaded from
 		github automatically.  To disable this package, use
 		"--disable-sc-hs-sky130".

 	--enable-sc-ms-sky130[=<path>]
 		The path to the sky130_fd_sc_ms library, a core PDK
 		library containing the medium-speed standard cell layouts
 		and data.  If the configuration option or the path is
 		not specified, then the library will be downloaded from
 		github automatically.  To disable this package, use
 		"--disable-sc-ms-sky130".

 	--enable-sc-ls-sky130[=<path>]
 		The path to the sky130_fd_sc_ls library, a core PDK
 		library containing the low-speed standard cell layouts
 		and data.  If the configuration option or the path is
 		not specified, then the library will be downloaded from
 		github automatically.  To disable this package, use
 		"--disable-sc-ls-sky130".

 	--enable-sc-lp-sky130[=<path>]
 		The path to the sky130_fd_sc_lp library, a core PDK
 		library containing the low-power standard cell layouts
 		and data.  If the configuration option or the path is
 		not specified, then the library will be downloaded from
 		github automatically.  To disable this package, use
 		"--disable-sc-lp-sky130".

 	--enable-sc-hd-sky130[=<path>]
 		The path to the sky130_fd_sc_hd library, a core PDK
 		library containing the high-density standard cell layouts
 		and data.  If the configuration option or the path is
 		not specified, then the library will be downloaded from
 		github automatically.  To disable this package, use
 		"--disable-sc-hd-sky130".

 	--enable-sc-hdll-sky130[=<path>]
 		The path to the sky130_fd_sc_hdll library, a core PDK
 		library containing the high-density, low-leakage standard
 		cell layouts and data.  If the configuration option or
 		the path is not specified, then the library will be
 		downloaded from github automatically.  To disable this
 		package, use "--disable-sc-hdll-sky130".

 	--enable-sc-hvl-sky130[=<path>]
 		The path to the sky130_fd_sc_hvl library, a core PDK
 		library containing the high-voltage standard cell layouts
 		and data.  If the configuration option or the path is
 		not specified, then the library will be downloaded from
 		github automatically.  To disable this package, use
 		"--disable-sc-hvl-sky130".

 	--enable-alpha-sky130[=<path>]
 		The path to the sky130_ml_xx_hd library, a third-party
 		library containing layouts of alphanumeric characters
 		for adding text to layout.  If the configuration option
 		or the path is not specified, then the library will be
 		downloaded from github automatically.  To disable this
 		package, use "--disable-alpha-sky130".

 	--enable-xschem-sky130[=<path>]
 		The path to the SKY130 setup for the xschem schematic
 		entry/schematic capture tool.  If the configuration
 		option or the path is not specified, then the library
 		will be downloaded from github automatically.  To disable
 		this package, use "--disable-xschem-sky130".

 	--enable-sram-sky130[=<path>]
 		This 3rd party library contains pre-compiled and verified
 		memory blocks from the OpenRAM open source memory compiler.
 		It is disabled by default due to the length of time
 		required to install, but it is recommended if you will be
 		using SRAM in a design.  If the path is not specified,
 		then the library will be downloaded from github automatically.

 	--enable-osu-t12-sky130[=<path>]
 		This 3rd party library is a set of open-source digital
 		standard cells at 12 track pitch height.  If the path is
 		not specified, then the library will be downloaded from
 		github automatically.

 	--enable-osu-t15-sky130[=<path>]
 		This 3rd party library is a set of open-source digital
 		standard cells at 15 track pitch height.  If the path is
 		not specified, then the library will be downloaded from
 		github automatically.

 	--enable-osu-t18-sky130[=<path>]
 		This 3rd party library is a set of open-source digital
 		standard cells at 18 track pitch height.  If the path is
 		not specified, then the library will be downloaded from
 		github automatically.

 	--prefix=<path>
 		This redirects the installation destination.  open_pdks
 		installs into ${prefix}/share/pdk/, and by default
 		${prefix} is /usr/local.  Be advised that Makefile
 		automatically adds the "share/" path regardless.  To
 		install in a different location, pass these (optional)
 		environment variables to "make":

 		SHARED_PDKS_PATH = <path>
 			Overrides ${prefix}/share/pdk/ and installs
 			directly into the specified <path>

 		DESTDIR = <path>
 			When defined, then "make install" installs into
 			the specified <path>.  However, all references
 			to files in the PDK will reference SHARED_PDKS_PATH.
 			Use DESTDIR if you want to install into a temporary
 			location such as a git repository or tarball that
 			will eventually be distributed and placed at
 			SHARED_PDKS_PATH on the target systems.

 Step 2:
 	Run:

 	    make

 	This will pre-process the setup files to create the PDK-specific files
 	for the SKY130A PDK, and process all vendor files, and place everything
 	in a local staging area (subdirectory sky130/sky130A and/or
 	sky130/sky130B).

 Step 3:
 	Run:

 	    [sudo] make install

 	This copies all files from the staging area into the
 	destination target.  All pointers to absolute paths in the
 	files are changed to match the local path.

 Step 4:
 	Any time you want to check if there are updates to repositories
 	that have been automatically pulled for open_pdks, Run:

 		make update

 	to pull any recent changes from the git repositories, and then
 	rebuild the PDK.

 Step 5:
 	After installation, the staging area is no longer needed and can
 	be removed with

 		make clean
 	or
 		make veryclean  (also removes the log files)

 	If you have not specified the installation to make symbolic links
 	back to the repository sources, then the sources are no longer
 	needed, either, and may be removed using

 		make distclean

 	However, doing so means that if the PDK needs to be updated and/or
 	rebuilt, the sources will have to be re-cloned from their public
 	repositories.

 	If at any time you want to remove the PDK, make sure you have run
 	the "configure" script to enable the PDK you want to remove, and
 	then do:

 		make uninstall

 -------------------------------------------------------------------------------
 Summary of the installation directories:

     The Makefile script takes the source files and generates files for local
     PDK names "SKY130A", "SKY130B", etc.

     The definition of each PDK is made in the Makefile using defines; e.g.,
 	-DMETAL5, etc.

     The make script makes use of the python script "preproc.py" (in the ../common
     directory) to parse each source file for "#ifdef ..."-type macros.  The syntax
     is similar to that used by the C preprocessor (cpp) but does not assume C
     language syntax in the input file, so is generally better to use than cpp
     (has less unexpected/unintentional behavior).  See comments in the preproc.py
     script for a full list of macros that it accepts (short list: #ifdef, #ifndef,
     #define, #include, and boolean operators ||, &&, and !).

     Files generated:
 	.tech		techfile for magic (full DRC, extract, GDS)
 	-GDS.tech	techfile for magic, vendor mask layers
 	.tcl		PDK script for magic
 	-BindKeys	key binding script for magic partly matching Cadence defaults
 	.magicrc	magic startup script (copy to local directory as .magicrc)
 	_setup.tcl	netgen setup script for LVS
 	.sh		qflow master setup script, standard 1.8V digital
 	.par		graywolf setup file, standard 1.8V digital

     The installation directory below LOCAL_PATH is the name of the PDK;  e.g.,

 	    sky130A/		5-metal stack with MiM cap and redistribution layer

     The installation directory hierarchy below the PDK name looks like the following:

 		libs.tech/		technology and setup files

 		    magic/		magic techfiles, startup file, PDK script,
 					and key binding script.
 		    netgen/		netgen setup file
 		    qflow/		qflow scripts and graywolf setup files.
 		    klayout/		setup files for klayout
 		    openlane/		setup and supplementary files for openlane
 		    ngspice/		base model files and libraries for ngspice
 		    xschem/		setup files for xschem
 		    irsim/		setup and parameter files for IRSIM

 		libs.ref/		foundry data

     Each subdirectory of libs.ref is further divided into sections based on the
     IP libraries.  The section names are foundry-dependent.  For SkyWater Sky130,
     these sections include one or more of:

 		    sky130_fd_sc_hd/		1.8V digital logic (high density)
 		    sky130_fd_sc_hdll/		1.8V digital logic (high density low leakage)
 		    sky130_fd_sc_hs/		1.8V digital logic (high speed)
 		    sky130_fd_sc_hvl/		3.3V digital logic
 		    sky130_fd_sc_lp/		1.8V digital logic (low power)
 		    sky130_fd_sc_ls/		1.8V digital logic (low speed)
 		    sky130_fd_sc_ms/		3.3V digital logic (medium speed)

 		    sky130_fd_io/		Standard I/O

 		    sky130_fd_pr/		Primitive devices w/fixed layout

 		    sky130_ml_xx_hd/		Library of alphanumeric layouts

 		    sky130_sram_macros/		Library of SRAM macros
 		    sky130_fd_bd_sram/		Library of SRAM components

     Each IP library has subdirectories corresponding to library standard file
     formats.  These are the following (not all of them may be present in any
     given library):

 		        cdl/		CDL netlists
 		        doc/		Foundry documentation
 		        gds/		GDS files
 		        lef/		LEF macro files
 		        lib/		Timing files
 		        mag/		Magic files derived from GDS
 		        maglef/		Magic files derived from LEF macros
 		        spice/		SPICE netlists (ngspice compatible)
 		        techlef/	LEF technology files
 		        verilog/	verilog modules

     The target installation destinations assume the directory structure above.  Changing
     this requires editing the source files.
	------------------------------------
	open_pdks
	----------------------------------------
	Master PDK generator for SkyWater Sky130
	Hybrid 180nm / 130nm foundry process
	for open source EDA tools
	----------------------------------------

	-------------------------------------------------------------------------------
	Quick summary (TL;DR):

	Prerequisites:

	sudo apt install python3

	The Magic VLSI layout tool is used often by the installation. If you do
	not have it, then obtain it and install with the following:

	sudo apt install m4 tcsh tcl-dev tk-dev

	git clone https://github.com/RTimothyEdwards/magic
	cd magic
	./configure
	make
	sudo make install

	Open_PDKs SKY130 Installation: Most people will want to run the following
	for PDK installation:

	./configure --enable-sky130-pdk
	make
	sudo make install
	make distclean

	This will download and install the SkyWater SKY130 PDK, the SKY130 setup
	files for xschem, a third-party library containing alphanumeric layouts,
	and others.

	With the above configuration line, the PDK files will be installed into
	the path
	/usr/local/share/pdk/sky130A/

	From open_pdks version 1.0.269, there is a process variant

	/usr/local/share/pdk/sky130B/

	which reflects support for ReRAM.

	-------------------------------------------------------------------------------
	Detailed instructions for the patient reader:
	-------------------------------------------------------------------------------
	Prerequisites:

	1. EDA tools:

	For installing files to use with the Magic layout tool, Magic must be installed.
	Obtain Magic from:

	https://github.com/RTimothyEdwards/magic

	No other tools are required for installation, although open_pdks will
	generate and install the setup files for a number of tools.

	2. Foundry source files [optional]:

	If you do not have the foundry source files, the latest versions of
	each library will be downloaded from github, and installed locally into
	the open_pdks/sources/ directory. If you have the foundry source files,
	then you can pass the location of each library repository to the
	open_pdks configure script. The instructions below are needed ONLY
	if you intend to download and install the PDK sources outside of
	open_pdks. Instructions below are only valid for the SkyWater SKY130
	process. For other open-source PDKs, instructions can be found in the
	corresponding README file in that PDK directory.

	Obtain sources for the SkyWater sky130 130nm process from the git repository
	at the following location:

	https://github.com/efabless/

	As of open_pdks version 1.0.428, the Sky130 sources are no longer under
	a single umbrella repository, so each core library must be downloaded
	individually. The individual core repositories are:

	https://github.com/efabless/skywater-pdk-libs-sky130_fd_pr
	https://github.com/efabless/skywater-pdk-libs-sky130_fd_io
	https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_hd
	https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_hdll
	https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_lp
	https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_hs
	https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_ms
	https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_ls
	https://github.com/efabless/skywater-pdk-libs-sky130_fd_sc_hvl

	This repositories may go in any convenient location. To keep the overhead
	low, you may install only the repositories that you need. At a minimum, the
	I/O library, primitive devices, and the high density and high voltage
	digital standard cell libraries should be installed. The remaining standard
	cell libraries are optional, as needed for low-leakage, high speed, low power,
	etc., applications.

	Then follow the instructions below for generating the additional files
	for supporting the open source EDA tool flows.

	PDK Installation:

	Step 1:

	Run "configure" to set the paths to the Google/SkyWater source
	repositories and to set the path to the install location. Note that
	the configure script is located in the open_pdks top level directory,
	not in the foundry subdirctory, and should be run from the top level
	directory. The primary configure options are as follows:

	--enable-sky130-pdk
	This is mandatory for specifying that the installation
	is for the SKY130 PDK.

	--with-sky130-variants=all\|A\|B
	When set to "all" (which is the default), both variants
	sky130A and sky130B are generated and installed. If
	only one PDK variant needs to be installed, then use
	this option to restrict the installation to a single
	PDK variant.

	--with-sky130-link-targets=none\|source
	"none" copies files from the source directories to
	the target. "source" makes symbolic links to the source
	directories. Use "source" only if doing a local install,
	and the source foundry data will not be deleted. For
	distribution installations, the value must be set to
	"none".

	--with-ef-style
	This option should not be used except in the context
	of the Efabless "open galaxy" platform where it is
	used. The default is "no". There are some differences
	in these two styles, the most important of which being
	that the order of directories for the IP libraries
	is <file_format>/<library_name> instead of
	<library_name>/<file_format>. Other differences
	include version tracking of the Magic setup files
	and the location of the technology LEF file.

	--enable-primitive-sky130[=<path>]
	The path to the sky130_fd_pr library, a core PDK
	library containing the primitive device models and
	layouts. If the configuration option or the path is
	not specified, then the library will be downloaded from
	github automatically. To disable this package, use
	"--disable-primitive-sky130".

	--enable-io-sky130[=<path>]
	The path to the sky130_fd_io library, a core PDK
	library containing the padframe cell layouts and data.
	If the configuration option or the path is not specified,
	then the library will be downloaded from github
	automatically. To disable this package, use
	"--disable-io-sky130".

	--enable-sc-hs-sky130[=<path>]
	The path to the sky130_fd_sc_hs library, a core PDK
	library containing the high-speed standard cell layouts
	and data. If the configuration option or the path is
	not specified, then the library will be downloaded from
	github automatically. To disable this package, use
	"--disable-sc-hs-sky130".

	--enable-sc-ms-sky130[=<path>]
	The path to the sky130_fd_sc_ms library, a core PDK
	library containing the medium-speed standard cell layouts
	and data. If the configuration option or the path is
	not specified, then the library will be downloaded from
	github automatically. To disable this package, use
	"--disable-sc-ms-sky130".

	--enable-sc-ls-sky130[=<path>]
	The path to the sky130_fd_sc_ls library, a core PDK
	library containing the low-speed standard cell layouts
	and data. If the configuration option or the path is
	not specified, then the library will be downloaded from
	github automatically. To disable this package, use
	"--disable-sc-ls-sky130".

	--enable-sc-lp-sky130[=<path>]
	The path to the sky130_fd_sc_lp library, a core PDK
	library containing the low-power standard cell layouts
	and data. If the configuration option or the path is
	not specified, then the library will be downloaded from
	github automatically. To disable this package, use
	"--disable-sc-lp-sky130".

	--enable-sc-hd-sky130[=<path>]
	The path to the sky130_fd_sc_hd library, a core PDK
	library containing the high-density standard cell layouts
	and data. If the configuration option or the path is
	not specified, then the library will be downloaded from
	github automatically. To disable this package, use
	"--disable-sc-hd-sky130".

	--enable-sc-hdll-sky130[=<path>]
	The path to the sky130_fd_sc_hdll library, a core PDK
	library containing the high-density, low-leakage standard
	cell layouts and data. If the configuration option or
	the path is not specified, then the library will be
	downloaded from github automatically. To disable this
	package, use "--disable-sc-hdll-sky130".

	--enable-sc-hvl-sky130[=<path>]
	The path to the sky130_fd_sc_hvl library, a core PDK
	library containing the high-voltage standard cell layouts
	and data. If the configuration option or the path is
	not specified, then the library will be downloaded from
	github automatically. To disable this package, use
	"--disable-sc-hvl-sky130".

	--enable-alpha-sky130[=<path>]
	The path to the sky130_ml_xx_hd library, a third-party
	library containing layouts of alphanumeric characters
	for adding text to layout. If the configuration option
	or the path is not specified, then the library will be
	downloaded from github automatically. To disable this
	package, use "--disable-alpha-sky130".

	--enable-xschem-sky130[=<path>]
	The path to the SKY130 setup for the xschem schematic
	entry/schematic capture tool. If the configuration
	option or the path is not specified, then the library
	will be downloaded from github automatically. To disable
	this package, use "--disable-xschem-sky130".

	--enable-sram-sky130[=<path>]
	This 3rd party library contains pre-compiled and verified
	memory blocks from the OpenRAM open source memory compiler.
	It is disabled by default due to the length of time
	required to install, but it is recommended if you will be
	using SRAM in a design. If the path is not specified,
	then the library will be downloaded from github automatically.

	--enable-osu-t12-sky130[=<path>]
	This 3rd party library is a set of open-source digital
	standard cells at 12 track pitch height. If the path is
	not specified, then the library will be downloaded from
	github automatically.

	--enable-osu-t15-sky130[=<path>]
	This 3rd party library is a set of open-source digital
	standard cells at 15 track pitch height. If the path is
	not specified, then the library will be downloaded from
	github automatically.

	--enable-osu-t18-sky130[=<path>]
	This 3rd party library is a set of open-source digital
	standard cells at 18 track pitch height. If the path is
	not specified, then the library will be downloaded from
	github automatically.

	--prefix=<path>
	This redirects the installation destination. open_pdks
	installs into ${prefix}/share/pdk/, and by default
	${prefix} is /usr/local. Be advised that Makefile
	automatically adds the "share/" path regardless. To
	install in a different location, pass these (optional)
	environment variables to "make":

	SHARED_PDKS_PATH = <path>
	Overrides ${prefix}/share/pdk/ and installs
	directly into the specified <path>

	DESTDIR = <path>
	When defined, then "make install" installs into
	the specified <path>. However, all references
	to files in the PDK will reference SHARED_PDKS_PATH.
	Use DESTDIR if you want to install into a temporary
	location such as a git repository or tarball that
	will eventually be distributed and placed at
	SHARED_PDKS_PATH on the target systems.

	Step 2:
	Run:

	make

	This will pre-process the setup files to create the PDK-specific files
	for the SKY130A PDK, and process all vendor files, and place everything
	in a local staging area (subdirectory sky130/sky130A and/or
	sky130/sky130B).

	Step 3:
	Run:

	[sudo] make install

	This copies all files from the staging area into the
	destination target. All pointers to absolute paths in the
	files are changed to match the local path.

	Step 4:
	Any time you want to check if there are updates to repositories
	that have been automatically pulled for open_pdks, Run:

	make update

	to pull any recent changes from the git repositories, and then
	rebuild the PDK.

	Step 5:
	After installation, the staging area is no longer needed and can
	be removed with

	make clean
	or
	make veryclean (also removes the log files)

	If you have not specified the installation to make symbolic links
	back to the repository sources, then the sources are no longer
	needed, either, and may be removed using

	make distclean

	However, doing so means that if the PDK needs to be updated and/or
	rebuilt, the sources will have to be re-cloned from their public
	repositories.

	If at any time you want to remove the PDK, make sure you have run
	the "configure" script to enable the PDK you want to remove, and
	then do:

	make uninstall

	-------------------------------------------------------------------------------
	Summary of the installation directories:

	The Makefile script takes the source files and generates files for local
	PDK names "SKY130A", "SKY130B", etc.

	The definition of each PDK is made in the Makefile using defines; e.g.,
	-DMETAL5, etc.

	The make script makes use of the python script "preproc.py" (in the ../common
	directory) to parse each source file for "#ifdef ..."-type macros. The syntax
	is similar to that used by the C preprocessor (cpp) but does not assume C
	language syntax in the input file, so is generally better to use than cpp
	(has less unexpected/unintentional behavior). See comments in the preproc.py
	script for a full list of macros that it accepts (short list: #ifdef, #ifndef,
	#define, #include, and boolean operators \|\|, &&, and !).

	Files generated:
	.tech techfile for magic (full DRC, extract, GDS)
	-GDS.tech techfile for magic, vendor mask layers
	.tcl PDK script for magic
	-BindKeys key binding script for magic partly matching Cadence defaults
	.magicrc magic startup script (copy to local directory as .magicrc)
	_setup.tcl netgen setup script for LVS
	.sh qflow master setup script, standard 1.8V digital
	.par graywolf setup file, standard 1.8V digital

	The installation directory below LOCAL_PATH is the name of the PDK; e.g.,

	sky130A/ 5-metal stack with MiM cap and redistribution layer

	The installation directory hierarchy below the PDK name looks like the following:

	libs.tech/ technology and setup files

	magic/ magic techfiles, startup file, PDK script,
	and key binding script.
	netgen/ netgen setup file
	qflow/ qflow scripts and graywolf setup files.
	klayout/ setup files for klayout
	openlane/ setup and supplementary files for openlane
	ngspice/ base model files and libraries for ngspice
	xschem/ setup files for xschem
	irsim/ setup and parameter files for IRSIM

	libs.ref/ foundry data

	Each subdirectory of libs.ref is further divided into sections based on the
	IP libraries. The section names are foundry-dependent. For SkyWater Sky130,
	these sections include one or more of:

	sky130_fd_sc_hd/ 1.8V digital logic (high density)
	sky130_fd_sc_hdll/ 1.8V digital logic (high density low leakage)
	sky130_fd_sc_hs/ 1.8V digital logic (high speed)
	sky130_fd_sc_hvl/ 3.3V digital logic
	sky130_fd_sc_lp/ 1.8V digital logic (low power)
	sky130_fd_sc_ls/ 1.8V digital logic (low speed)
	sky130_fd_sc_ms/ 3.3V digital logic (medium speed)

	sky130_fd_io/ Standard I/O

	sky130_fd_pr/ Primitive devices w/fixed layout

	sky130_ml_xx_hd/ Library of alphanumeric layouts

	sky130_sram_macros/ Library of SRAM macros
	sky130_fd_bd_sram/ Library of SRAM components

	Each IP library has subdirectories corresponding to library standard file
	formats. These are the following (not all of them may be present in any
	given library):

	cdl/ CDL netlists
	doc/ Foundry documentation
	gds/ GDS files
	lef/ LEF macro files
	lib/ Timing files
	mag/ Magic files derived from GDS
	maglef/ Magic files derived from LEF macros
	spice/ SPICE netlists (ngspice compatible)
	techlef/ LEF technology files
	verilog/ verilog modules

	The target installation destinations assume the directory structure above. Changing
	this requires editing the source files.