ECE 425: Introduction to VLSI System Design Machine Problem 0 Due: Friday 11:59pm, Sep. 15th, 2017

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1 ECE 425: Introduction to VLSI System Design Machine Problem 0 Due: Friday 11:59pm, Sep. 15th, 2017 You will spend most of your lab time using the Virtuoso design tools from Cadence Design Systems. Virtuoso is a set of tools for full-custom silicon chip design, giving complete control over all design aspects to you, the designer. It has long been the industry leader in its class. This tutorial will introduce you to entering designs into Virtuoso, before you begin designing anything original. Our designs will consist of layouts, schematics, and Verilog code. A layout is a complete physical description of a chip, the three-dimensional pattern which may be fabricated on a wafer of silicon. A schematic diagram represents the components formed by the layout in a two-dimensional format. Although a one-dimensional text file is sufficient to simply list the chip s components (such a file is called a netlist), schematic diagrams enable you to draft a design in two dimensions before starting the laborious layout process. This advantage makes schematics the standard for custom circuit design. In this MP, you will be following two tutorial documents, where you will learn how to create schematics and layouts using Virtuoso. By the end of this tutorial, you will have created your own accumulator schematic, inverter layout and 2-input mux layout. You will need to submit the PDFs for the ones you create following the tutorials, not the master layouts given to you for reference. You may help each other and ask for help. Please use Piazza so that all help is shared as much as possible. We will use Linux exclusively in this class. Linux is more popular than Windows in engineering, and its more advanced features are very helpful in digital circuit design, so it s a good idea to learn it well. Please direct Linux questions to the technician in the EWS lab rather than the TA s. If you already know Linux well enough, you may also choose to log in from home. Cadence Design Framework II Virtuoso stores designs in a database system managed by the Cadence Design Framework. This means that you cannot access your data in UNIX files without exporting them first. Although it is tempting to manage your projects and files using Linux, Cadence will work better if you do things its way: 1. Always launch Cadence directly from your work directory. 2. Do not edit directories (libraries and cells) managed by Cadence. 3. There is one exception: Cadence creates temporary files to track who is editing what part of the database. After a crash, the files will be locked as if someone else is editing them. To unlock all your files, run this from your work directory: find. -name \*cdslck -exec rm {} \; Setup Please keep all coursework in your work directory, /home/your_netid/ece425.work. Always enter your 1

2 ece425.work directory before starting any work. To begin the tutorial, initialize your work directory with the following commands: cd ~ mkdir ece425.work cd ece425.work mkdir ece425mp0 cd ece425mp0 mkdir comptut cd comptut module load cadence/aug2016 cp -r /software/cadence- Aug2016/IC617/tools/dfII/samples/tutorials/composer/*. (Attention: There is a dot. at the end of the command!) (The cp command is in one single line) cp ~ece425/.cdsinit. cp ~ece425/.cdsenv. cp ~ece425/.cdsplotinit. cp /software/ncsu-cdk beta/cdssetup/simrc. The Cadence Documentation Viewer Invoke the Cadence reference library with the command cdnshelp &. You will find the needed information by typing the keywords or clicking along the document tree. The documents related to MP0 are in the following locations: Composer Tutorial: ~ece425/comptut.pdf Cell Design Tutorial: ~ece425/celltut.pdf Please copy the two pdf files to your own folder and follow the instructions from tutorial files to do MP0. cd ~/ece425.work cp ~ece425/comptut.pdf. cp ~ece425/celltut.pdf. 2

3 Part 1: Schematic Design Entry (Composer Software) Composer Tutorial 1. Open comptut.pdf file. 2. Follow the instructions and complete Chapters 1 to 5 inclusive (starting on page 13 of the PDF file or under the title Starting the Schematic Composer Software in the HTML) of the composer tutorial with the following notes: Note: The comptut.pdf is written for the older version of Virtuoso, so some details will be slightly different from the new version we are using in this class. We have added notes in the PDF file (highlighted in yellow) with some of updated instructions with different menu names. We have updated all changes on first and/or second occurrences but may have not placed the updates on all repeating places so please refer to the prior note if you don t find the listed menu options. Neglect the command of icfb in the pdf. All we are using is the command virtuoso On Windows and Linux, you will be able to view the notes we added in tutorial PDF files by default, but on Mac OSX, you may need to enable options to view the contents: Mac OSX: open file on Preview. Select View->Highlights and Notes on menu bar and notes will show up on left side of the window. If you encounter the following pop up window while opening any schematic, select Always. -OR- Figure. Sample screenshots of pop-up window regarding license warning. Chapter 1: 1. Start with Starting the Cadence Software 2. Be sure to go into the directory of ~/ece425.work/ece425mp0/comptut/ before launching Cadence software 2. Execute module load cadence/aug2016 and type virtuoso & from the directory of ~/ece425.work/ece425mp0/comptut/ to launch the Cadence. 3. Library Path Editor window will pop up as the software launches. If not, select Tools->Library Path Editor from CDS.log window. 4. Manually add the 8 libraries according to paragraph 2, section Setting the Paths to the Tutorial Libraries in Chapter 1. Replace the your_install_dir with /software/cadence-aug2016/ic617 3

4 when adding the path of the 8 libraries. You can simply neglect /your_home_dir/comptut since TTL_tutor, master, tutorial, and user_asic are under current directory. After adding the 8 libraries, the Library Path Editor should be like this (the ordering of the library doesn t matter): Chapter 2: Start with Opening the Schematic Window. Figure. Library Path Editor screenshot Chapter 4: Ignore Creating a Sheet Border and Title section. 4

5 Print to File: 1. The Accumulator schematic in PDF format. To print the schematic, use File => Print... in the schematic window. You must print to a file (Check Send Plot Only To File under Plot Options). Make sure to turn off the Header and Mail Log options, and change the page size to be letter instead of A4. Sample configuration windows are shown as follows. The software will print to an EPS format file (e.g. accum.eps ). You could use the following command to turn it into a PDF file: ps2pdf accum.eps There will be a new pdf file named accum.pdf generated. We will talk about how to merge all the pdf files into single pdf report at the end of this document. Note: Please do NOT use screenshot. Points will be deducted for screenshot with black background with unreadable zoom setting! Figure. Plot options setting screenshot 5

6 Part 2: Layout Design and Verification (Virtuoso Layout Editor and Diva Software) Cell Design Tutorial 1. Execute these commands: cd ~/ece425.work/ece425mp0 cp -r ~ece425/cell_design*. cd cell_design module load cadence/aug2016 cp ~ece425/.cdsplotinit. cp /software/ncsu-cdk beta/cdssetup/simrc. virtuoso & 2. Open celltut.pdf file. 3. Follow the instructions from Chapter 1, Opening Designs, through Chapter 4. Note: (1) The celltut.pdf is written for the older version of Virtuoso, so some details will be slightly different from the new version we are using in this class. We have added notes in the PDF file (highlighted in yellow) with some of updated instructions with different menu names. We have updated all changes on first and/or second occurrences but may have not placed the updates on all repeating places so please refer to the prior note if you don t find the listed menu options. Neglect the command of icfb or layoutplus in the pdf. All we are using is the command virtuoso (2) To switch layers in the current tool (page 83, Changing to metal2 ), you have two ways to do that: a. manually layout a wire and add via by yourself. The option of "Change to layer" is essentially the same with inserting a via. It just automatically insert the via for you. For example, when you need to change from metal 1 to metal 2, double click the end coordinate the path, choose "Create--Via--M2_M1", and put the via at the end of the path. Then, change the active layer to metal 2 and continue with the path. b. create shape -> geometric wire, when drawing the wire, right click to bring up the contextual menu, and choose via up/down to add a via and switch layers. 6

7 Print to File: 1. The Inverter layout (clearly label all pins) in PDF format. 2. The Multiplexer layout (clearly label all pins) in PDF format. Refer to the printing instruction in Composer Tutorial. Although you do not have to finish the Cell Design Tutorial to get the printouts specified above, you should go through the whole tutorial to familiarize yourself with the Virtuoso Layout Editor, since you will need to spend most of your time on laying out your cells for the next two MPs. Merge All PDF Files into a Single Report Please refer to the following sample command to merge all the PDF files to a single file, and only turn in the merged PDF file. The command below will merge three different files: in_1.pdf, in_2.pdf, in_n.pdf file into single out.pdf in the order specified. Make sure to merge the designs in order we have listed in the document (e.g. MP0: 1. Accumulator schematic, 2. Inverter layout, 3. Multiplexer layout). : pdfunite in_1.pdf in_2.pdf in_n.pdf out.pdf What to Submit: Single PDF file (mp0_netid.pdf) containing following items in order 1. Accumulator schematic 2. Inverter layout 3. Multiplexer layout 7