Tutorial 1: Initial set up and Voltage Divider.

Start MobaXterm


This is your command terminal which is used to access the Cadence server

To connect to the server type in the command window "ssh -Y -C <your_assined_name>@yiyanli.fortlewis.edu" and then press enter( see sample below)


You will now be asked to type in your temporary password. When you are typing in your password nothing will display on the screen.

The following will appear:


Retype your temporary password to get the following couple of lines.  Nothing will display as you are typing your password.


Now Type in your new password it must meet these requirements:

This ensures that the terminal will not freak-out at you and that your account is secure. 

When done correctly your connection will be closed


To re-login type in the terminal window "ssh -Y -C <your_assined_name>@yiyanli.fortlewis.edu" and press enter. Or recall the previous command by pressing up arrow and then enter.
Type in your new password and the following will appear:


Now, in the command window type in "clear" then enter to clear the command window.




                                                       Using the Command Window

WHEN ITS TIME LOGOUT TYPE IN THE COMMAND WINDOW "EXIT" THEN PRESS ENTER IF THAT DOES NOT WORK, IN THE COMMAND WINDOW PRESS "CTRL AND C"

In the terminal you will need to know a few commands now that initial set up is done.
To run a command type in the command in and then press "enter" or "return"

This place is called your home directory. This is where you will navigate from to setup and start Cadence.
The "~" will change to indicate your current directory. "~" is your home directory.  Directories are case sensitive. 

Now the directory is Users. 

The "cd" command will take you from any directory and return you back to your home directory.
Below the cd command is taking me from Users back to my home directory ~



To move up a directory type "cd .."  then press enter



To view directories that you are able to move down into type in the command window "ls", to view everything in a directory including hidden files type "ls -la"



To move down a directory type cd <namedirecotry>  and press enter.

In the sequence below I use the "ls" command to see which directories I can move to.  Then I type  "cd Users" to move down the Users directory. 

Finally I type " cd <username>" and low and behold I'm back to my home directory


"pwd" is a very useful function.  When typed into the terminal it displays the entire path to your location. This is the absolute path to my home directory (underlined in red).

To get help on any command type " <command> --help". Using "cp --help" , where "cp" is the is the copy command we get:


In most cases it will tell you the usage of the command and all of the arguments that can be used with the command (underlined in red)

       Getting Cadence and Virtuoso started. 

1.) Edit the .bashrc file

Navigate to your home directory.   

.bashrc is a hidden file. To see it type "ls -la" in to the command window.


To edit, type into the command window "vi .bashrc" or "nano .bashrc" or use your favorite txt editor.

Add the following to the .bashrc file.

export CDSHOME=/cadence/
export MMSIMHOME=/cadence/SPECTRE181/
export PATH=$CDSHOME/tools/bin:$CDSHOME/tools/dfII/bin:$MMSIMHOME/tools/bin:$MMSIMHOME/tools/dfII/bin:$PATH
export CDS_AUTO_64BIT=ALL
export LD_LIBRARY_PATH=$AMSHOME/tools/lib:$CDSHOME/tools.lnx86/lib:/usr/lib:/usr/dt/lib:/usr/openwin/lib:
/usr/lib:$AMSHOME/tools/lib:/usr/dt/lib:/usr/openwin/lib:$CDSHOME/tools.lnx86/lib:$AMSHOME/tools/lib/
64bit:$AMSHOME/tools/lib:$LD_LIBRARY_PATH

export CDS_LIC_FILE=5280@obelisk.srv.fortlewis.edu
export SPECTRE_DEFAULTS=-E
export CDS_Netlisting_Mode=Analog
export CDS_LOAD_ENV=CWDElseHome
export CDK_DIR=/4Tbhardrive/ncsu-cdk-1.6.0.beta

The final file should look like this:


Save then quit the .bashrc file. 

To re-initialize the file type ". .bashrc" into the command window

We will now copy over CMOSedu to your home directory.

Copy  it over to your home directory using the command   "cp -r /4Tbhardrive/CMOSedu   <Your home direcotry> "        (where r means recursive)

To determine your home directory use the "pwd" command. Below is how to determine everything from scratch using only the commands we know how to do.  The last "ls"  is to see if there is a CMOSedu directory in our home directory.

     

 Navigate into to the CMOSedu that is now in your home directory.  

Add the following lines to cds.lib file using your favorite txt editor.  

DEFINE analogLib /cadence/tools.lnx86/dfII/etc/cdslib/artist/analogLib

DEFINE functional /cadence/tools.lnx86/dfII/etc/cdslib/artist/functional

DEFINE sbaLib /cadence/tools.lnx86/dfII/etc/cdslib/artist/sbaLib

The finished file should look like this:



The cds.lib are where the cadence libraries are defined. 

Set the simulator default to "spectre" open the .cdsenev file. Then change the simulator from "hspiceD" to "spectre".

                HOW TO START

To start Virtuoso navigate to the CMOSedu and type "virtuoso &" in the command window

"&" will allow you to still use the command window.

If you get an error:


Then navigate back to your home directory and type ". .bashrc" into the command window, Then navigate back to CMOSedu and type "virtuoso &"

 TO LOGOUT, CLOSE CANDENCE THEN,TYPE IN THE COMMAND WINDOW "EXIT" THEN PRESS ENTER

Voltage Divider Tutorial1

 Log on to the Cadence server by navigating to CMOSedu and typing "virtuoso &" into the command window.



Two windows will appear on your screen.  In order they are the Command Interpreter  Window and the Library Manager. The Command Interpreter  Window (CIW) is  where  commands, reports, and errors  will be printed. The Library Manager is where all of your saved instances can be found.
( The windows have been resized for the tutorial)




In the Library Manager mouse over to  "file" then to "New"   and click on "Library"


Open MobaXterm and navigate back your home directory and use the pwd command. This will be the save path for the new library.


In the " Create Library" window pick a name for tutorial 1 ( names cannot have spaces in them), for the path put down the path that was found using the pwd command. 
Change the technology Library to "attach to existing tech library"  and pick the library used by the professor. I used AMI 0.60u. Then press ok.





You can now see that the tutorial has been added to the list of libraries.

Click on Tutorial_1 then go to "file" then to "New" then to "Cell View". This is how we will creating the most of the cells that we need. 

 

We will call the cell "R_div". Make sure that view is schematic and the type is also schematic, and click ok. 


A warning window will pop up, in it click "Always".


The next window will be where we will be placing down components to build the voltage divider.

To start laying down components press "i" or click on    button.

In the window that pops up use the drop down menu to change the Library to "NCSU_Analog_Parts". In cell type "res" to get a resistor. 



Press Hide to start placing down your resistors,  Left click to place and right click to rotate.  Use the mouse wheel to zoom in and out, press in the mouse wheel to drag the work space.   Press "f" to automatically resize the window. 

Press"ESC" to cancel.  To undo press "u"


Now we will need a voltage source press "i" to bring up the " Add instance" window change the cell to "vdc" (voltage dc source)


Set the DC voltage to 1. (where the red lines are). If the lower part of the window does not appear click below the " Rotate button"


Click hide and place down the voltage source.   Press after placing the voltage source press and "ESC" then  press "i'  and change the cell the gnd for ground the view will change symbol.

The final circuit should look like something like this:


To change the options for a component, click on the component and press "q".  Change the resistance to 10 K ohms and press ok. Change the other resistor to 10 K Ohms as well.


To wire components together press "w" or click on . The completed circuit should look as follows.



Onced wired click on " Check and save"  return to the CIW and double check that there are no errors.

To label wires to the schematic click on  which will bring up the wire label menu.

Name the wire "in" then press hide and click on wire leading into the R1 resistor.  Name another wire "out" and put it on the output of the R1 resistor. Click on check and save when finished.


We are now going to launch the simulation software. Mouse over to "Launch" and click on  "ADE L" .



A pop up window will appear click on always.  


To confirm that  simulator is "spectre"   mouse over to Setup then click on Simulator/,,,,

In the popup window confirm that the simulator is "sptectre". Then press "ok".   



To set up the type of analyses, mouse over to Analyses and click on "Choose". In the popup window set "Analysis to "tran" with a stop time of 1 (units are in seconds), click enable. Press "ok"
 

To plot save and plot signals click on "Outputs" then click on " To Be Saved"  then "Select on Design"

Go back to schematic and click on the wire labeled "in" and the wire labeled "out".  When a wire is selected, the wire and the wire name will turn a different color.



In the Outputs window click the plotted boxes.  The final ADE window will look like this


Once everything is set up click run .  Once the simulation is complete two new windows will pop up. The first, is a log of everything that happened, it will contain information about CPU usage and time to run the simulation.  This window is only needed if there are errors while running your simulation. 


The other view is the plot with our inputs and outputs. Our input should be at 1V and because this is a voltage divider our output will be at .5V.



Close out of the plot. 
This was just a test to view and learn the analysis tool.  save the  set up by clicking on "Sessions" and "Save State"
In the new window set the save state option to "cell view", Then press "ok". Once the view has been saved close the ADE window. 



Return to the schematic and delete the voltage source and the wires connecting it.  The schematic should look as follows. 


To add pins to schematic press "p" or button.  Name the first pin "in" and make sure the Direction is set to "input". Press hide and place the "in" pin on the "in"wire   Name the second pin "out" and make sure the direction is set to "output".
After the schematic should look like as follows.  When finished click on "check and save". There should be no errors reported in the CIW.  


We are now going to create a symbolic view of this design. To begin, click on "Create" then to "Cell view"  then "From Cell view". 

In the pop up window make sure that the view name is "symbol". Then press "ok".
 
In the next pop up window press "ok"


The view that is generated by automatically by the Symbol tool is not really help full. We will draw our own symbol for the schematic that we just created. 
To do this, delete everything but the pins. When finished it should look as follows.


To move the labels out of the way press "m"  and then click and move the label. Click and dragging does not work.  Press "ESC" to close out of the current tool.
 
Now click on "Create" then to "Shape" then to "Line". A new window will pop up, click on "Hide". To draw, click on where you want to start then click on the next point and a line will be drawn.  To stop drawing double click on the point where you want to stop,
The first resistor should look something like below. 


Once the first one has been drawn, draw the second resistor and a ground symbol.  The final drawing should look something like as follows.   When you are finished Check and Save the Symbol.  


Now we are going to create a simulation library where only the files necessary to the simulation live.
Close out of both the symbol view and the schematic view.  In the Library Manager, right click on the R_div and then click "Copy". In the copy window change the two cell to "sim_R_div", Then press "ok".
  
Now delete "spectre_state1" and "symbol". To do this right click on the View and click on "Delete".  In the pop up window make sure that everything is correct then press "ok",then "yes"


Now open the schematic view in sim_R_div and delete everything in it.  We are going to replace it with the symbol that we just drew. Press "i" and bring up the component selector.  Change the Library to " Tutorial_1"
Change the cell to "R_div". Press "Hide" and place the symbol in the schematic. 


Add a power source,  ground, and wires.  The  power source is 1V.  All of the parts are found in the NCSU_Analog_Parts.  When you are done it should look like this:


Check and save.  Note there are warnings. To view the warnings mouse over to "Check" then to "Find Marker".  We will figure out the errors here. 


To zoom to an error check the "Zoom To Markers" box then click on the error you wish to view. The errors that are on the "out" pin and on the "out" wire are because they are floating, meaning they are not connected to anything.    In our case we can ignore the errors. To do this click on the ignore button and a start(*) will appear next to the ignored errors.   When the errors have been ignored click "Apply" then close the window. Then run another check and save.  Now there are no errors. 
Now re-analysis the circuit.  Using the same procedure as before open ADE L and set it up to run the same simulation as before. 


As we can see in the plot, the output voltage is .5V, so nothing has changed.  Save the state by going to "Session" then to "Save State". Change the box to cell view and save it under sim_R_div.

Before we move on let us see how we can descend through the hierarchy in the drawing.  In the sim_R_div schematic click on the voltage divider symbol.  While it is selected mouse over to "Edit" then to "Hierarchy" then to " Descend Edit"


After its been click a pop up window will appear, here you can pick where you want the view to be.  For simplicity, change the bubble to "new tab" then press "ok".

We now have two tabs.  The first tab is the schematic and the second tab is the schematic that represented by the symbol. This is very useful you have to make quick edits to the underliying  schematic, or when you need to remind yourself of what is in the symbol. 


Close out of both of those drawings.

We are now going to layout a resistor.
Return back to the library manager and have Tutproal_1 highlighted.  Mouse over to  "File" then "New" then " Cell View".  


In the pop up window, call the cell "R_N_well_10K" in the view section remove "schematic" and type "layout". The "type" will automatically change.  Then press "ok" . In the next pop up window click on "Always" just like before. 



On the left had side we have all the layers that we can use to make circuits.  For the resistor we will use the nwell layer. 
 
Now mouse over to "Options" then  to "Display".  In the Display Options menu we want to set a couple setting that will make our live easier.  First we want to check Pin Names under Display Controls,  Then we want to change our display level from 0 to 10.  To save these as our defaults forever click on "file" then press "Save To". Then press ok to leave the settings. 
                               

Make sure the nwell layer is selected and then press "r" this will allow you to draw a rectangle.  Press hide on the pop up menue. Draw one rectangle  of any size. 



We want resistor that is 56 um long and 4.5 um wide.  Click on one of the green boxes and press "q" this will allow us to change its properties.  Modify the dimensions so that it is with in these constraints. When you are done press "ok"  For example I changed the dimensions to as follows.


Now we need to check our work.   Mouse over to "Verify"  then click on "DRC".

In the DRC pop up window 
press ok to start the DRC analysis.

Open the CIW to see how many error and what type of errors they are. In my case I have 4 errors and they are that my rectangle is not on the grid.  Every layout you do must pass DRC without any errors.

To fix these errors we first need to figure out my grid spacing to do that mouse over to "Options" then click on "Display". Here we see that X and Y Snap Spacing is .15. Then close out of the window. 

Now we need to adjust the dimensions of the rectangle to fit on this spacing. The length of the resistor is 56 and 56/.15 = 373.33 which is not a hole number so we need to get as close as we can.  For the width we used 4.5 and 4.5/.15 = 30 which is a whole number, so in my cause I had to change mine to what is seen below.
 
And now when I run DRC I get no errors. 
Don't forget so save when needed.
Now we need to add pin connections to the nwell.  Press "i" and change the library to "NCSU_TechLib_ami06" and change the cell to "ntap".


Press hide and place the ntap so that the edge is barley touching the nwell resistor. 
The final resistor should look like the following:

Switch to metal1. Now we will add pins to the Layout. The pins are found in a dropdown menu next to . See the red circle in the picture below. 


In the create pin menu, the terminal name will be L and check the box "Create Label".
 

Press hide and draw a box around the blue portion of the left ntap. Then place the label. The Right side will have the label R.  When this is done mouse over to "Options" then to "Display" and change the display level stop to 0. This will show the layer that you have added. Your completed resistor should look something like below.  When the stop level is 0.


After checking reset the stop level to 10.  Now DRC. 
There should be one error in the CIW.  The computer does not know that this is a resistor.  We have to label it is such.  In the layer selection window scroll down unit you see "res_id"

We are now going to draw a rectangle over the resistor that we had previously drawn.   With res_id selected press "r" to draw a rectangle.  You will see little resistor symbols fill in the area as you draw the rectangle.  The finished resistor should look like this:


Now run a DRC and there should be 0 errors. 
To extract the view mouse over to "Verify" then click on "Extract".   In the window that pops up press "ok"
An extracted view is now is your library, open the extracted view from the library manager.


In the extracted view we can see how close we were to creating resistor that is very close to 10K ohms. We are unable to exactly reach 10K ohms due to constraints in manufacturing and also because variability in the nwell layer. 



Close the extracted and layout views.

We are now going to build the layout for the voltage divider.
In the R_div cell open a new layout,  in the layout place two 10K nwell resistors.  DRC the new layout to ensure there is enough space in-between the resistors


 




Should look something like this:


Now we are going to add metal for the connections.  Select metal1 and user to draw the rectangles.  Once you are done, DRC the layout. 


Add pins to the new metal1 layers.  They will be named "in", "out" and "gnd".  Use metal1 as the pin metal and make the pin rectangles the same size as the original metal layers.  Make sure Create Label is checked. 

Save, DRC, and Extract your layout. 
Now we are going to run an LVS which is layout versus schematic. 
Mouse over to "Verify" and click on "LVS"

In the pop up window  click on Browse and select the extracted view that we just created. Then Browse for the original schematic. They both will be in cell R_div




Click on "Run" and the LVS will run it might take a moment. If another window pops up asking to save press "ok".   You can watch it in the CIW.   When the LVS has finished you might see a pop up window,  which will display the results of the LVS. If you do not get a pop up window, the CIW will also display the results of the LVS.
"The net-lists failed to match"  means the LVS failed and the layout is not the same as the schematic.
To get a more detailed result of the LVS click on "Output"

From the detailed view we can see that there are 3 main errors.



The first one we will tackle is "Terminal gnd! in the schematic is not present in the layout."   In most layout views we need to have a global ground.  Global is indicated by ! . 

In the layout view click on the gnd pin and press "q" to bring  up the options.  You might have to move the metal1 layer out of the way to get to the pin metal1 layer. Change the name of the pin from "gnd" to "gnd!"





 Open the schematic from the R_div cell. Click on the pins and press"q" we can see that the direction of the pin is input.  If we return back to the layout we and get the options of the "in" pin we can see that its direction is  input/output.

We need to change the layout pin to input. 









We need to do the same thing on the "out" in the layout, except we need to change it to output to match the schematic. 
When that is done don't forget to save. Now we need to extract the layout like we had done earlier.  Now run another LVS, this time the netlist should match.  If we look at the click on output we can see that everything is fine and dandy. 
If you still get "netlist does not match" after running the new LVS then double check that you used all of the same syntax for you pins in the schematic.   LVS is case sensitive.
When you get a successful LVS you have finished the first tutorial!!!
 Make sure you master the basics in this tutorial such as placing objects (adding an Instance), creating  new layouts and schmatics  using the library manager, moving objects around,  placing pins in both layouts and schematics, and placing down metal in a layout.