Scripting for EDA tools

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Scripting for EDA tools

• Building chips is very expensive
• Remember, this is about making money
• Incredible complexity (dont mess up!)
• Many, many steps (dont forget anything)
• Need one recipe that everybody can use (many
  cooks)
• Need to document the process (who did what, how?)
• Can we do it over.. exactly the same way?
• Scripting allows us to take care of all these
  issues.
• Real world ASICs are built this way.

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Scripting for EDA tools

• What is a script?
• A series of statements in a text file that tell
  the computer what to do.
• The statements are interpreted by a command
  interpreter or shell.
• Statements can be normal control flow or calls to
  other programs or scripts. (scripts can call
  scripts)
• They use some language
• You have used them but may not know it.
  (makefiles)

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Scripting for EDA tools

• Scripting environments
• C shell (csh), TC shell (tcsh), Bourne shell
  (sh), Bash shell (bash), are very general purpose
  shells.
• PERL, Python, TCL are very general purpose
  scripting languages.
• TCL drives most CAD tools (Synopsys, MGC)
• Some tools have proprietary scripting language,
  e.g. Cadence Skill language
• nix CAD tools usually driven by a command
  interpreter (shell). Hence, dc_shell-xg-t

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Scripting for EDA tools

• General purpose scripting language differences
• TCL
• Very simple
• Easy to learn
• Fairly powerful
• Usually embedded in CAD tools
• Often augmented with specialized commands for the
  tool

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Scripting for EDA tools

• General purpose scripting language differences
• PERL (Practical Extraction and Reporting
  Language)
• Extremely powerful
• Very popular, flexible
• Swiss Army Chainsaw of scripting languages
• Easy manipulation of files, processing textual
  information
• PERL gives you 5 ways to do anything
• Can be very cryptic, and hard to learn
• Strong cult following
• Learn it from the web

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Scripting for EDA tools

• General purpose scripting language differences
• BASH Shell (Bourne again sh)
• Linux command interpreter
• Flexible, powerful
• Good manipulation of files, controlling programs
• Not too hard to learn
• Learn it from the web

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Scripting for EDA tools

• What scripting gives us
• Automated chip build process
• Repeatability
• Documentation of the build process
• No GUIs to learn
• Fast built times
• Management of directories and files produced
• Freedom to go for coffee while build is running
• One day I realized that sadness is just another
  word for not enough coffee. Wally (Dilbert)

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Scripting for EDA tools

• When to use the GUI
• First time through the tool
• First try at simulating a module
• With whatever you do, capture the transcript file
• The transcript file once renamed and edited is
  the beginning of your tool (TCL) script

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Writing Bash shell scripts

• Bash shell scripts are text files
• Text files most efficiently built with
  programming editors (emacs or vi)
• File must be executable and in search path
• chmod 700 my_script
• PATH environment variable may not include .!
• An example shell script
• !/bin/bash
• My first script
• echo "Hello World!"

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Writing Bash shell scripts

• Compile a VHDL file with vcom (script doit1)
• !/bin/bash
• if ! d work then
• echo work does not exist, making it
• vlib work
• fi
• if ! s averager.vhd then
• vcom averager.vhd
• fi
• work directory must exist before compilation

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Writing Bash shell scripts

• File attribute checking
• !/bin/bash
• if ! s junk_file then
• mkdir junk_file
• Fi
• Spaces around brackets are needed!
• File attribute checking
• -d exists and is a directory
• -e, a file exists
• -f exists and is a regular file
• -s file exists and is not empty

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Writing Bash shell scripts

• Compile VHDL then run a simulation..(script
  doit2)
• !/bin/bash
• if ! -d "work" then vlib work
• fi
• if ! -d "vectors" then mkdir vectors
• fi
• if -s "averager.vhd" then
• vcom averager.vhd
• vsim averager -do do.do -quiet c
• else
• echo vhdl file missing
• fi

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Writing Bash shell scripts

• vsim command and arguments
• vsim entity_name do dofile.do quiet -c
• -quiet do not report loading file messages
• -c console mode (no GUI)
• try vsim help for command line arguements

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Putting it all together

• TCL dofile do,do directs the simulation
• add list -nodelta
• configure list -strobestart 99 ns
  -strobeperiod 100 ns
• configure list -usestrobe 1
• add list -notrigger -hex -width 8 -label
  data_in data_in
• add list -notrigger -hex -width 8 -label
  data_out data_out
• add list -notrigger -hex -width 8 -label
  mux_select mux_select
• force -freeze clk 1 0, 0 50 ns -r 100
• force reset_n 0
• force data_in X"00"
• force mux_select 1
• force data_in X"A5"
• force mux_select 1
• run 150
• force reset_n 1
• run 50
• force mux_select 0

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Putting it all together

• What did the simulation write out?
  (averager.list)
• ns data_in data_out mux_select
• 99 A5 00 1
  
• 199 A5 00 1
  
• 299 A5 29 0
• 399 A5 52 0
• 499 A5 7B 0
• 599 A5 A5 0
• Could we compare this data against another file?

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Putting it all together

• Compare against a golden vector file (script
  doit3)
• !/bin/bash
• clean
• .....as before, but add..
• if ! s vectors/golden then
• echo comparison vectors do not exist
• exit
• else
• diff vectors/averager.list golden gt report
• fi
• if ! -s "vector_report" then
• echo " "
• echo "HOORAY IT WORKS!"
• echo " "
• else
• echo " "
• echo "BOO HOO HOO, ITS BROKEN!
• fi

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Putting it all together

• File redirection
• gt write to file, but no clobbering
• gtgt append output
• gt clobber (overwrite) the file

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Putting it all together

• Shell variables
• Example OSU_syn_lib nfs/guille/a1/cadlibs/osu
  _lib
• Usage
• vlog OSU_syn_lib/lib_ss_1.62.v work work
• dollar sign dereferences the variable

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Putting it all together

• Case conversion
• Ex cat vectors/averager.list tr a-z A-Z gt
  tempfile
• mv tempfile vectors/averager.list
• Split output
• vcom my_module.vhd work work tee compile_log
• output goes to screen and to the file

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Intro to PERL

• Larry Wall at NASA, late 1980s
• Needed a tool to make report processing easier
• PERL and the webs need for text processing made
  PERL really take off
• PERL is now found on most any computer system
• Online documentation, tutorials, examples abound
• Excellent reference OReillys PERL in a
  Nutshell

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PERL basics

• Perl statements are separated by semicolons
• 2 Basic data types numbers and strings
• number 100000
• string collection of chars inside or
  quotes.

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PERL quoting

• String literals delimited by single or double
  quotes
• Double quoted string literals are subject to back
  slash and variable interpolation, and single
  quoted strings are not. (except for \ and \\)
• Single and double quotes can be written as q
  for single quotes and qq for double quotes.
• The brackets serve as the delimiters.

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PERL quoting

• PERL Quoting can be made clear

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PERL quoting

• double quote
• suffixqq.txt
• command quoting
• print qxls grep suffix
• When the script is run, we get
• leopard traylor ./scr.pl
• loc.txt
• tmp1.txt

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PERL Data Types and Variables

• Variables three basic types
• scalars (things), arrays(lists),
  hashes(dictionaries)
• Scalars are simple variables
• preceded by a dollar sign ()
• a scalar is either a number, string or reference
  (think pointer)
• Do not have to specify if a scalar is a number or
  a string. Perl determines this from its usage.

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PERL Data Types and Variables

• Arrays are ordered lists of scalars accessed with
  a numeric subscript. Subscripts start with zero.
• Arrays are preceded by an at sign (_at_).
• Hashes are unordered lists of key/value pairs
  accessed by using the keys as subscripts.
• Hashes are preceded by a percent sign ().

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PERL Data Types and Variables

• Variables always begin with the character that
  identifies its type , _at_ or .
• Upper and lower cases are distinct.
• Variables are given values with the equals sign
  ().
• crn57141 assigns the number 57141 to crn
• _at_date (8, 24,70) assigns list to array date

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PERL Data Types and Variables

• Scalar variables always begin with the character
  , even when referring to a scalar value that is
  part of an array. i.e., fruit_at_fruit_array2
• Every variable type has its own namespace. For
  example junk is distinct from _at_junk which is
  distinct from junk.

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PERL Data Types and Variables

• An array is a variable that stores an ordered
  list of scalar values that are numbered starting
  at zero.
• Negative indexes count backwards from the last
  element in the list. i.e. (-1 refers to the last
  element in the list)
• Example _at_count(5,8,23)
• count2 is equal to 23
• count-1 is equal to 23
• count-2 is equal to 8

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PERL basics

• Math and operations with strings
• Examples
• a8 a holds the string 8
• ba 1 b equals 9, evaluated as numbers
• ca.1 dot(.) is the string concat operator
• d5050
• Perl converts stings to numbers as needed
• b evaluates to a number because of the
  operator
• c evaluates to 81 because of the concat
  operator
• d is equal to 100 even though both 50s are
  stirngs!

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PERL control flow

• Loops
• for(i0 ilt15 i)statement block
• Conditionals
• if if(expression)statement block
• else statement block
• While Loop
• while (ltINFILEgt)print ltOUTFILEgt, _\n

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PERL File I/O

• A filehandle is the name for an I/O connection
  between Perl and the OS filesystem.
• Convention is to use uppercase names.
• All Perl programs automatically open three file
  handles STDIN, STDOUT, and STDERR.
• By default, print and write functions write to
  STDOUT.
• Other file handles are created by
• open filename.txt for reading
• open(FILEHANDLE,filename.txt)

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PERL File I/O

• To open for writing or appending
• open(OUTFILE,gtfilename.txt)
• open(OUTFILE,gtgtfilename.txt)
• Check for successful file opening by
• open(FILEHNDL,file)die(open failed)
• or
• open(FILEHNDL,gtgtfile)warn(oops!)
• die terminates the program and warn writes a
  message to standard error.

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PERL File I/O

• Once the file is opened, you access the data
  using the diamond operator, ltFILEHANDLgt. This is
  the input line operator. It returns a line from
  the filehandle as a string.
• Each time its called, a new string is fetched and
  is placed in the special variable _.
• Close files when you done by
• close FILEHNDL