that you can save your session as a cell view ?

I am sure that you are familiar with saving ADE sessions. But I have seen some students

save it as a Directory instead of a Cell View. The advantage of saving it as a cell view is that you can open the saved session from Library Manager by double clicking on ‘spectre_state1‘ under Cell views column ( you will see this below schematic, layout etc under Cell View). When you save it as a Directory, you’ll have to Open ADE, and then load the saved session. The simplest way is to save it as a Cell View. Try it out the next time you do your lab.

that you can disable the annoying pop-ups during copy, move, etc ?

In the main ICFB Log window, click on Options > User Preferences.

Then, you need to uncheck the option “Option Displayed When Commands Start“. However, you’ll have to turn this back on if you plan to use the options given in the pop-up menus.

Map schematic to layout

After you have built the schematic, you can map it to get a skeleton structure of the layout. Don’t expect it to give you fully layout material. The tool is capable of selecting the standard layout views of nmos and pmos transistors and put them into the layout tool. The way to do that is :

Click on Layout XL, and Create New.

I have taken the example of a 2 input NOR. So, enter the cell name and click on OK. Virtuoso Layout XL will now open up and click on Design > Gen From Source …

By default the pins are in p-well layer, which you need to change to metal1 or allot whatever layer you want each pin  to be on. Click on OK.

You’ll see a boundary box (in purple), inside which you need manually place each of the nmos and pmos instances. Note that  the layout of nmos and pmos instances have been taken from the associated Techfile. Next you can place the pins on the edges of the purple boundary. Wait ! There’s a neat way to do this,
click on Placement > Pin Placement.

Arrange and setup the options as shown. You can click on Interleave and it will arrange the pins in an alternate fashion. Or click on each pin, change the Edge (to left, right, top or bottom) and click on Apply. For gnd! and vdd!, after clicking on Apply, you can convert it into a H-rail or V-rail by clicking on the appropriate button. Then when its ready, click on Close. In the main Layout window, you can click and drag each nmos/pmos instance into the boundary box. As you do that, you’ll notice flylines that show the connectivity between the pins. Also, you’ll see that the same component will get highlighted in your schematic window ( that’s because these two are properly mapped). Try CTRL-F to see the original layout and the metal layers of the instances.

Happy layouting !

How to create a Bus ( wide wire)

Here, the subtractor is implemented using single wires. The comparator has been compressed using the bus.  So, if you need to create a pin that would support a  bus, it should have the name as ‘name<0:11>’ and connect it with a wide wire and remember to name the wide wire as well. Then you can tap individual lines from the wide wire as shown in the subtractor’s case as ‘sub_rpm<0> ,sub_rpm<1> ..etc’. And if you need to view/plot the signals in the graph, you can simply click on the bus and all the lines will be added to the list of things to be plotted.

that you can automate instead of sourcing the license every time ?

This is a very basic Linux tip and specifically for ASU students. I have seen a lot of people log into the linux servers and then do :

$> cd cadence5

$> source /usr/local/../ncsu.cshrc

An easier way to go about this is to create a file called .cshrc in your home directory (~ character indicates home dir, or if you type ‘cd’ and enter, that will take you to your home directory). Execute the following commands in the linux prompt.

$> echo “cd cadence5” > ~/.cshrc

$> echo “source <license_path> ” >> ~/.cshrc

Now, you can directly start icfb and skip the above two commands after the xterm/terminal comes up.

that you can edit Library paths through cds.lib ?

Library Manager shows you the list of available libraries that has valid schematics and cell views. You can change the library path as shown.

You can change the path of a library through cds.lib .  There’s a file called cds.lib which lies in the folder from where you start ICFB. So what the tool does is, it will check for cds.lib within the current working directory and update the paths in the Library Manager. If you start ICFB from some other folder that does not have any cds.libs in it, then you’ll probably get an empty library. So, to change the path, open the current working directory through the terminal and edit the cds.lib file.

If you want to hide a particular library, you can comment out the entire line by putting a # prefix like below :

#DEFINE <library_name> <path>

Now, you can hide all those libraries that you have used in your previous semesters and keep your Library Manager clean.

that you can simulate without loading GUI ?

Have you come across this situation before – the xterm that you use to connect is very slow and it takes time to load the GUI version of icfb, select the library, schematic and then the ADE to simulate the design ? Well, if you have the design ready and simulated it before through ADE, you can save it as an OCEAN script. Then you can run the same through the OCEAN shell which in turn calls Spectre.

Now, you can run the script instead of opening the GUI version. At your Linux prompt, type in “ocean” and enter. the Ocean prompt will open up and then load the script :

 

Its important that you enter the command exactly as shown. Any extra space here or there will result in an error.