Lab 1 SERDES: Cadence Basics

The premise of this lab is for you to:

  1. Get you used to using Cadence Simulation

  2. View an Eye Diagram

You will find that there are some similarities to Vivado.

There are some annoyances with the copy / paste, but I’ll show you how to deal with that.

Pre-requisites

  1. Go get access to the Cadence tools

    • Create an account using your school email at nanhub.org

    • Go to: https://nanohub.org/groups/cadence_access and request access

    • Wait to be accepted

Let’s Get Started

My entry is always:

  • https://nanohub.org/groups/cadence_access

Click on Digital Implementation

Now. Before we start, on the Top Right click on Go to Access Wave this will open the Cadence Tools in a new tab in a Windowed Full Screen. (A lot more pleasent to look at)

Open the Left menu bar. You’ll find the clipboard tab as well.

Open a Terminal if there’s not already one open.

There’s 2 ways to import the folder you need

  1. Git Clone (Easy)

    • You will use the clipboard tab

  2. Create a Zip-File of the Folder and import it

    • You will need to move the folder once you import it

    • For when youi have a local folder and don’t want to make a github repo

We’ll be using the Git Clone method.

You won’t be able to ctrl + v into the terminal.

Paste what you want into the box and click the clipboard icon on the top left.

../../../../_images/clipboard_ss.png
Use:

  • git clone https://github.com/maganamon/CARP_Labs_Tutorials.git

You will only need the SerDes_Labs Directory

I have a bunch of useless folders and files so you can get rid of them with:

  • rm -rf FOLDER_NAME

  • rm FILE_NAME

Now cd chain yourself all the way to:

  • SerDes_Labs -> Lab1_Parrallel_vs_Serial -> SerDes_TxRx

Now we’re going to open Xcelium using the terminal with:

  • Make sure it’s all 1 line. I split it for website formating reasons.

xrun -64bit -sv -access +rwc -gui -top tb_top_level_serdes Serializer_tx.sv Deserializer_rx.sv
top_level_serdes.sv tb_top_level_serdes.sv

The file after -top indicates the toplevel module.

All other listed files are the modules that the top level will need.

I have already written a basic Serializer and Deserializer then had ChatGPT write the Testbench.

Congrats

The simulation should now be open.

Note

“Send to Waveform”

  1. Add All DUT (Top Level) Signals

  2. Dut -> Serial

  • Add loaded_data, counter

What we will learn

  • Sim Console “run XXXns”

  • Moving by Edge

  • Under “Cursor” tab. Changing Radix

  • Follow the Hex 55 Example

  • Colors, Groups, Dividers

  • Search for Values

Eye Diagram Time

../../../../_images/viva_meme.jpg

Virtuoso: ViVa where ViVA stands for Virtuoso Visualization and Analysis Tool

Open Up that Bash Terminal again and run:

  • viva &

  • Give it a minute cause that ‘ish is slow

Click the Folder Icon on the Left under the Browser tab.

  • Expand the folder on the botton until you get to the Top_Level Folder.

  • Click it, and look for the serial_data signal. Double Click the Signal.

You should see the signal and a bunch of 0 and 1 wave forms.

  • Click the Measurements tab at the very top

  • Then click Digital to Analog

Logic High: 1 V Logic Low: 0 V Rise Time: 1ps Fall Time: 1ps

We have created essentially a perfect circuit with these parameters.

  • Click the Measurements tab again at the very top

  • Then click Eye Diagram

  • Unit Interval for 100Mhz Clk = 10ns

The Unit Interval tells Cadence how often to chop up the waveform and overlay them on top on each other

  • Finally click plot eye

You should see something like this:

On the Right is the eye diagram, and on the left the Analog signal (When we went from Digital to Analog)

notice… That doesn’t look like an eye? Why is that?

That’s all for today. Lab 2 we’ll see the real eye diagram.