Mentor Graphics Tutorial

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Table of Contents

Page Number

Introduction and Objectives 3

Running the Software for the First Time 4

Project Creation Using ASIC Design Kit 6

Setting up Simulations 13


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Introduction and Objectives

Mentor Graphics provides one of the most well known commercial IC design software in the world. The department of Electronic Engineering at Princess Sumaya University for Technology has subscribed the license file for IC Nanometer Design tool from Mentor Graphics. The software tool provides the options of design and simulation integrated circuit layout and parasitic extraction for highly accurate circuit design. This tutorial will give a brief introduction on how to use the software tool to design the circuit schematic and do the simulation.

For circuit schematic design and simulation, ASIC Design Kit Design Architect IC (ADK_DAIC) and ASIC Design Kit IC (ADK_IC) are used. In the following sections we will learn how to draw the circuit schematic using ADK_DAIC and deploy a layout for the design using ADK_IC and run the simulation using ELDO.

You need a student account to login to the lab computer. There is a default user name and password for the lab computers. If you need the login information, contact our network Administrator (Eng. Munther Zabin) or the course teaching assistant (Eng. Hazem Marar).


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Running the Software for the First Time

First time user: Running the software in a healthy organized environment requires a creation of folders within a specific hierarchy. Thus, being a first time user, create a folder in your home directory so that you can save all your files in and use them later. Go to the student directory where you have the access permission to create and manage folders and create a folder with your name. On the terminal you can type the commands to create a folder cd /home/student mkdir your_name

Create a project folder (library): To put your work files in an organized manner, each time you start a new project create a separate folder for it (i.e. an inverter project, an adder project …). Your first project is going to be an inverter, thus create a directory in your main folder where you can save all your project files. On your terminal type the commands to create a project directory inside your folder. cd /home/student/your_name mkdir Inverter This folder can be assumed as your own library in which you create your own design.

Creating Cells for your Schematic and Layout Files: Your schematic and layout files are going to be saved in folders “Cells”. Each cell should only contain one schematic. To start with your project we need two cells, one for the design schematic and one for the simulation “Test Bench Cell”. To do this you need to type the following in your terminal cd /home/student/your_name/Inverter mkdir VLSI_Inverter cd /home/student/your_name/Inverter mkdir VLSI_Inverter_TB

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Project Creation using ASIC Design Kit: Once you log into the computer, open the terminal and type the following commands: tcsh source /etc/profile.d/mg.sh adk_daic This will initiate the Design_architect_IC window from where you can create your projects, schematics, layouts etc. the window should appear as follows


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NOTE: At this point make sure that you get no error messages in the status bar at the bottom of the software window.

Creating the schematic: To start creating your schematic choose “Open-> Schematic” from the File menu as seen below

The “Open Schematic” dialog will appear as seen in the figure below. Click on the browse button and browse to your schematic folder which we name previously “VLSI_Inverter”. Make sure that you open it in editable mode.

When you click the “OK” button you have created a schematic file inside the cell called “VLSI_Inverter”. The program screen should now appear as seen below.


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As seen from the program, it is divided into four sections. The first section is the workspace; in which you place the components needed and connect them through wires to create the entire schematic. The second section is the options pane. In here you will find some useful shortcuts as delete, copy, undo…etc. these options are also found under the menus in the program.

The third section is the menu bar. These menus contain all the needed functionality to control your design. There exist several commands and functions which are advanced and are out of the scope of this tutorial. The commands that we are going to use will be mentioned during the text.

The fourth right sided pane “Edit Palette” contains necessary operations which are used during the design such as simulating the final design.

Now we are going to start designing the inverter. As you know, an inverter consists of one NMOS and one PMOS transistor. Thus, we should start by inserting these two transistors. To do this, click on “ADK IC LIBRARY” from the “Edit Palette” as seen in the figure below.


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A new side pane will appear where you can all the components you need such as NMOS, PMOS, capacitors, resistors…etc. Add an NMOS transistor and a PMOS transistor to the workspace as follows

The next step will be connecting the transistors’ terminal to form an inverter. To do this choose “Add -> Wire” and connect the required terminals. At this point so far, the schematic should look like the figure below.


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Note that when placing different components, they have default properties in terms of size, length, width…etc. To change these default settings and parameters click on an instant (component) and then press the “Q” button on your keyboard. A new pop-up window will appear containing all the parameters of that component. When changing these parameters, make sure to enter acceptable values, since, in some cases, the program will not warn you if you have entered an invalid value, and thus errors will appear in late simulation results. Thus, always make sure to enter a valid value for a certain parameter.

A professional design method that you should follow is to design the inverter as we did without connecting any supplies or input signals to it. Instead, you will create a symbol, just like a block diagram or a black box that is an inverter and includes all the transistors you used before. This black box will only have input and output pins where you can connect sources to. So, first we


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start with the pins, in our inverter case, we have four pins; an input pin, output pin, ground pin, and an operating voltage source pin. To add a pin click on “Add Pin” found in the left sided option pane as seen in the figure below. After that, rename each pin by clicking the “Q” button and changing its value to a desired name.

The final schematic of the inverter should look like this

Once you have done this, you have built your first inverter. To make sure that what you did was correct, click the “Save and Check” button in the menu bar. A window will appear and shows the results of the schematic test. In case of an error, a message will appear denoting the place where the error occurred and the nature of that error.


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After that, we have to create a symbol for our schematic. To do this, simply click on the “Miscellaneous” menu found in the menu bar and choose “Generate Symbol”. Be sure to choose “save and edit symbol” from the “once generate” in the window that appears.

After doing this, you will see an inverter just like a black box. Place it and save your work.


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As you can notice from the figure above, the inverter is now a black box. To see the transistor level all you have to do is to double click on the inverter, and that will take you to the transistor level back again. At this level only the four pins that we added are viewed. For these pins, we are going to connect the supply voltages and the input signal and observe the change on the output pin in the simulation mode. The simulation tool for the Mentor Graphics application is ELDO.

Setting-up Simulations: To start your simulation you need to create a new schematic file; a test bench file. To do this, click on “File -> Open” and then locate the “VLSI_Inverter_TB” folder that we created earlier. A new empty schematic file will be created. We need to ass the inverter that we designed. To do this, click on “Add -> Instance -> Choose Symbol” from the menu bar as below


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Locate the folder “VLSI_Inverter” and double click it. You will notice the inverter symbol being inserted to the schematic.

From the “Edit Palatte” pane insert the voltage sources and the input signal. Apply suitable values for their properties.

When finished, your design should look similar to this

To simulate the circuit you need to go to the simulation mode. Select ‘Simulation’ option on the “Edit Palette” and this will allow you to select model files, setup analysis mode, run the simulation and view outputs.

Select Model Libraries: From the Simulation window, select ‘Lib/Temp/Inc’ on the right side of the window. A new ‘Simulation Setup’ window will pop-up. In the ‘Scenario name’ text box type ‘typical’ and then click ‘Add …’ icon (this is the right top one icon in your ‘Simulation setup’ window). You will see the ‘typical’ in the list. Select the ‘typical’ from the list and browse for the model files.

Select the model libraries for the devices and components in your design. The model files are located at “/Mentor/adk3_1/technology/ic/models/tsmc018.mod”.


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Simulation Setup: Now select the ‘Analyses’ option from the ‘DA_IC’ window. A ‘Setup Simulation Analysis’ window will appear. This will give you to setup different types of simulation settings for your circuit. Select the ‘Transient’ check box and click ‘Setup’. This will allow you how long you want to do the transient simulation. Set 100 μ for the STOP time and a print time step of 1us.


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Define ports to view output: From the simulation window select the ‘Wave Outputs’ from the left sided shortcuts list. Select the following options Analysis TRAN Task Plot Type Voltage Now select input and output ports from the simulation window and you will see the N:IN and N:OUT in the ‘objects’ list of the ‘Setup Simulation’ window. Next press the icon ‘Add Wave Output’. Close the window and go back to simulation window.


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Successful Simulation: From the simulation window, press the ‘RUN ELDO’ option. Press OK one more time and you will see the simulation running. Once the simulation is completed you will see the message ‘Simulation Completed Successfully’ in the ‘Message Area’. You don’t get this message recheck all of your setup.


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View Simulation Output: Once your simulation is done, select the ‘View Waves’ from simulation window left sided shortcuts list. Expand the list under ‘VLSI_Inverter’. Select TRAN and then double click on V(IN) and V(OUT). You will see the input and output waveforms of the inverter.

DC or AC simulations can be done in the same manner. Multiple simulation types can be done at the same time.

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Mentor Graphics Tutorial