Custom IC Design

Things You Didn't Know About Virtuoso: IC 6.1.4 ADE Enhancements

2010-03-10T14:00:00Z

I'm not going to beat around the bush here. I could tell you about all the things that are new in ADE (Analog Design Environment) in IC 6.1.4. I could tell you about the fact that the individual subwindows are now resizeable, rearrangeable (is that a word?), undockable and tabbable (I know that's not a word, but it's fun to say) just like the assistants in the main Virtuoso window. I could tell you that the Parametric Analysis UI has been redesigned. I could also remind you to read my earlier post about all the new features added to ADE in previous IC 6.1 releases.

But I won't. Why? Because there is one new feature in ADE in IC 6.1.4 that tops all the others in terms of fulfilling widespread long-awaited user requests. Dependent expressions. Being able to use the name of one expression in others expressions based on it instead of having to repeat the entire definition of the first expression. No longer do you have to go cross-eyed trying to parse enormous paragraph-long expressions. Break them up into smaller, more sensible expressions and build from there. It's logical, it's intuitive and it's here today in IC 6.1.4.

There is a great video available here in the Cadence Online Support Video Library showing you how this works. I have a favorite example I use in demos. The original expression (which was created in IC 6.1.3) looks like:

((1 - (average((VT("/OUTM") - VT("/INM"))) / ((value((VT("/OUTM") - VT("/INM")) 4.3e-09) + value((VT("/OUTM") - VT("/INM")) 1.23e-08) + value((VT("/OUTM") - VT("/INM")) 2.03e-08) + value((VT("/OUTM") - VT("/INM")) 2.83e-08) + value((VT("/OUTM") - VT("/INM")) 3.63e-08) + value((VT("/OUTM") - VT("/INM")) 4.43e-08)) / 6))) * 100)

Egads! That 33 sets of parentheses (hopefully in the right places), and 7 repetitions of the expression (VT("/OUTM") - VT("/INM")). Not to mention I'm also interested in the values of several of the subexpressions individually (so those will have to be repeated again on their own).

So now in IC 6.1.4 that above expression can be created as:

((1 - (GainDiffAvg / GainDiffErr6Avg)) * 100)

where:

GainDiffAvg = average(GainDiff)
GainDiff = (VT("/OUTM") - VT("/INM"))
GainDiffErr6Avg = ((GainDiff_4p3 + GainDiff_12p3 + GainDiff_20p3 + GainDiff_28p3 + GainDiff_36p3 + GainDiff_44p3) / 6)
GainDiff_4p3 = value(GainDiff 4.3e-09), etc.

Granted, it's still pretty involved, but by breaking up the expression into more manageable bits, it's a whole lot easier to see what's going on (and to make sure you've got it right).

Expressions can be added in any order and can be based on any number of other expressions. No cyclic dependencies, please.

Hopefully, this improvement will help make it a bit easier to create the measurements your really interested in.

Stacy Whiteman

Things You Didn't Know About Virtuoso: Thumbnails

2010-03-03T14:00:00Z

Boy, you must think we're a few sandwiches short of a picnic over here at Cadence.

A couple of months ago we came out with this great new Virtuoso software release (IC 6.1.4). So, despite my best efforts to get you to use the recently-opened files list or to create bookmarks, the first thing you did after starting virtuoso was open the Library Manager. (Don't try to deny it, I know you did...).

So there's the Library Manager with your libraries all neatly grouped and color-coordinated, and down in the lower right corner of the window, there's now a little black square. You say to yourself, "Wow, that's the one new feature I was hoping for in this new release...a little black square in the corner of the Library Manager. Thanks, Cadence!". (Actually, you probably thought something not so suitable for a family-friendly blog such as this.)

Well, before you run off and start tweeting all your friends about how Cadence has had another brain fart, read on a bit and let me tell you how to unlock the magic of that little black box.

Thumbnails, my friends. Thumbnails are the wave of the future. And thumbnails are what that little black box is for. But first you've got to create them and that's why the box is empty right now.

So, to create thumbnails for the cellviews in your library, just RMB over a library name or a cell name or a schematic, symbol or layout view name and select "Update Thumbnails" (or select Edit->Update Thumbnails from the main menu).

Now the little box will contain a small image of the cellview so you'll know it's the right one without having to open it. These thumbnails will also appear when you use the File->Open... form to browse for a cellview.

So, now that we've begun exploring the wondrous diminuitive world of thumbnails, leave a comment to let us know where else you think thumbnails might be useful in the future...

Stacy Whiteman

Analog Behavioral Modeling - What Language Do You Speak?

2010-03-02T14:00:00Z

An increasing number of mixed-signal design teams are contemplating adding analog behavioral modeling to their repertoire in order to achieve reasonable simulation speeds. Utilizing analog behavioral models can yield simulation performance improvements that can make full chip verification a reality. This approach can be several magnitudes faster than transistor-level; however, the actual performance improvement is greatly dependent on the level of detail in the model, as well as, the language of choice. Analog behavioral models are generally written in one of the languages below:

Verilog-AMS – A derivative of Verilog, it includes analog and mixed-signal extensions in order to define the behavior of analog and mixed-signal systems, providing both continuous-time and event-driven modeling

Wreal – An extension of the Verilog-AMS modeling language allowing analog block operation as a real data flow model

Verilog-A – An extension of Verilog to describe analog and non-electrical behavior as a continuous-time subset

VHDL-AMS (IEEE1076.1) – similar in concept to Verilog-AMS, providing analog and mixed-signal extensions in order to define the behavior of analog and mixed-signal systems

One of the biggest challenges in the creation of analog behavioral models is; whose job is it? The analog designer is the most familiar with the circuit performance and specific behaviors, however, many analog designers typically are not programmers and familiar with the languages mentioned above. The digital designer, who also tends to be the full chip verification engineer, is most familiar with programming languages, but lacks the analog specific circuit knowledge. Therefore, a blend of both skill sets is required or a conscience effort for both designers to work together. One must continually make the tradeoff of effort versus benefit when deciding to create an analog behavioral model. Some of the questions that come to mind are: Can I re-use it? How long will it take me to create a high quality model? What performance gains can I expect?

Finally, as you consider adding analog behavioral modeling to your design repertoire; consider your modeling goals and language. A performance model needs to capture specific circuit behavior and can affect your effort versus benefit equation, while a functional model requires you to only capture the 1^st order effects that are needed to verify the circuit functionality. Model On!

Greg Curtis

Things You Didn't Know About Virtuoso: Options? What Options?

2010-01-25T14:00:00Z

Recently, I got involved in helping out a customer who had become frustrated using the "stretch" command in the Virtuoso Schematic Editor. They were posing all kinds of detailed questions about the different options to the command.

Options? The stretch command has options? You just grab the stuff you want to stretch, select the command, and then you...well, then you stretch. Oh, wait a minute, I remember now. Lots of Virtuoso interactive commands have an options form that is normally hidden, but can be brought up during the command with a function key. Quickly rummaging around in my brain, I determined that it was the F3 key. (Actually, I started the stretch command and then tried pressing the function keys, one at a time, until the form came up--F1 opens the manual, in case you were wondering).

For future reference, in IC 6.1, there is an icon on the "Create" toolbar (just to the right of the "Create Pin" icon) which brings up the options form. Also, you can force the options form to come up automatically by clicking the "Options Displayed When Commands Start" box in the CIW->Options->User Preferences... form (but that can get kind of annoying after a while, IMHO).

At this point, I spent the better part of the afternoon in "what does this button do?" mode exploring all the different combinations of options, the end result of which is the video below (as well as a few enhancement suggestions to R&D as to how to make some of the options a bit more intuitive).

I was truly amazed at how many little tidbits I learned in just exploring this one basic command. Hopefully you will too.

If video fails to launch click here.

Back to more new IC 6.1.4 features next time.

As always, your tips, comments and feedback are welcomed!

Stacy Whiteman

Virtuoso Layout Migrate - 614 Enhancements

2010-01-12T00:00:00Z

Hi, I'm Thibault Alix and I have been working with the VLM team for two years. I'm going to present what's new in Virtuoso IC6.1.4.

Cadence® Virtuoso® Layout Migrate is the physical layout migration tool within the Cadence Virtuoso custom design environment. It supports fast process and design rule migration of hard IP, custom digital designs, mixed-signal blocks, memories, and standard cell libraries.

Below is an example of a design before and after migration using the VLM tool :

Illustration 1 : Memory bloc - source (180nm)

Illustration 2 : Memory bloc - target (90nm)

In order to optimize / migrate a design, the flow requires several steps :

Illustration 3 : Migration flow

Until IC613, the VLM standalone executable (Qtrek) was called at each step and communicated with Virtuoso using IPC through a SKILL interface :

Illustration 4 : Virtuoso / Qtrek communication

Those operations were time consuming, since Virtuoso and Qtrek were waiting each others' response after each operation.

In Virtuoso IC6.1.4, the SKILL layer has been replaced by a C++ interface. Because the code is integrated to Virtuoso, IPC is no longer used, which decreases the runtime.

Here is a benchmark test done on several designs to compare 613_ISR and 614. This test has been done on the same machine, and the values displayed are an average of three runs.

Design	Size (nm)	Tool	IC613_ISR	IC614	Improv.
standard cell A	1.5 x 3	VLM	50s	12s	x4
standard cell B	9 x 3	VYO	25s	5s	x5
standard cell C	12 x 3	VYO	25s	5s	x5
design A	47 x 14	VLM	47s	16s	x3
adc_sample_hold	100 x 68	VLM	1min14s	1min9s	x1.07
OP Amp	120 x 150	VYO	5min22s	5min15s	x1.02
design C	226 x 429	VLM	7h	6h35	x1.06

Along with this modification, the GUI has been recoded in C++, using the Qt library. It has been redesigned to ease user's operations, and helps him to analyze and solve migration results using the Annotation Browser.

Illustration 5 : Annotation Browser and VLM

Over 25000 lines of SKILL code have been converted into C++. The code is now more stable, readable, debuggable, and the architecture is such that we can quickly plug new functionalities (like the Interactive DRC Fix).

Thibault Alix

Things You Didn't Know About Virtuoso: IC 6.1.4 (VSE L)

2009-12-15T14:00:00Z

By now, you've surely heard the news. And if you haven't yet, you have now. Virtuoso IC 6.1.4 is now available! Huzzah, huzzah!

I was (and still am) planning to do my next series of "Things You Didn't Know" about ADE XL, but for now I feel I'd be remiss if I didn't pause and devote a few posts to the new features in IC 6.1.4. Those are very likely "things you don't know" since they are brand new.

Direct Text Editing--Virtuoso Schematic Editor (VSE) L

You won't notice much different about the appearance of the schematic editor, except for one icon on the Edit toolbar at the top of the window. It looks like a letter T with a pencil sitting next to it. When you click on this icon (or use default bindkey "t"), you enter text editing mode. Now move your mouse around the screen and watch the status display in the lower left corner of the window. When you pass over a piece of text on the screen that is editable, the display will tell you. Then all you have to do is click on the text and type to change the value.

You can edit wire names, pin names, instance names, notes and instance property values directly on the schematic canvas. Now, not only do you NOT have to bring up everyone's favorite bindkey "q" form, you don't even have to use the handy new Property Editor Assistant. Look at that transistor. See where it says "w=2u"? Want to change it? Just click and type. Callbacks and all that other magic will be taken care of automatically.

To exit text editing mode, just press the Esc key. Aaah, the Escape key. What would we do without it?

Dynamic Net Highlighting--Virtuoso Schematic Editor (VSE) L

Technically, this feature has been in Virtuoso for a few ISR releases now, but it is fairly well hidden and in 6.1.4 it has been "prettied up" a bit. Dynamic net highlighting is especially handy when you have a large schematic and/or when you've got a lot of connections-by-name (i.e. lots of little stubs of nets hanging off of pins with tiny little labels identifying which net they're connected to).

To turn this on, go to Options->Display... and turn on Dynamic Net Highlighting. Now you'll see when you hover your mouse over a wire, a colored halo will appear on all the segments of that net--all over the entire schematic. Say you've got an inverter in one corner of your schematic and the output of that inverter is just a stub. You want to know which blocks the output of that inverter is connected to. Just hover your mouse over the stub coming out of the inverter and all the other connections will be clearly visible. Note that the wire segment you're hovering over won't be halo-ed. It will be highlighted with a dotted line, just as it normally would be.

This feature has a few environment variables associated with it:

Whether it is on by default:

schematic schDynamicHilightOn boolean { t | nil }

What the highlight color is when the schematic connectivity is up-to-date (default is "magenta"):

schematic schDynamicNetHilightColor string hilight_color

What the highlight color is when the schematic connectivity is not up-to-date (schematic check needed) (default is "yellow"):

schematic schDynamicNetHilightColorAlt string hilight_color

Tip: Don't forget that while you're hovering over that net, you can just RMB to add a probe to the net, so the whole net will be persistently highlighted up and down the hierarchy regardless of what other objects you manipulate.

More Good Stuff: In 6.1.4 Bookmark capabilities are now available in the basic L level of VSE. Look for File->Bookmarks in the schematic banner menu. While you're in that File menu, you'll also see that the recently-opened design history list is now available there too, just as it is in the CIW File menu (which you should hopefully have been using for a while now).

Lots more new features next time...

Stacy Whiteman

Things You Didn't Know About Virtuoso: ViVA (Part 4 of 4)

2009-12-03T14:00:00Z

Today, we're going to take on the somewhat daunting topic of the ViVA Calculator. But first, as usual, a digression. This time a trip down memory lane, or for most of you, more likely a history lesson...

Back in the days just after man discovered fire, my teacher brought something to class that looked like this. What an amazing thing! You could hold it in the palm of your hand and do math problems on it. Too bad I couldn't afford the $295(!) it would cost to buy one. I found a quote from the original manual: "Our object in developing the HP-35 was to give you a high precision portable electronic slide rule. We thought you'd like to have something only fictional heroes like James Bond, Walter Mitty or *** Tracy are supposed to own". (Funny, I don't recall James Bond doing logarithms all that often...)

Another exotic feature of HP calculators, as most people came to know, was something called RPN, or Reverse Polish Notation, something HP referred to as "the most efficient way known to computer science for evaluating mathematical expressions". For years it drew a dividing line between HP users and, for example, me.

I never learned to speak Reverse Polish, so when I opened the ViVA Calculator and saw the dreaded "Stack", I quickly averted my eyes and said, "In the interest of time, let's move on to the next part of the demo...".

But despair not, for I have braved the wilds of the ViVA Calculator and found that, armed with a few easy tips, anyone learn how to use it like a pro.

Push/Pull

First, let's talk a bit about how to get data into the Calculator. After all this calculator is for operating on waveforms, not just crunching numbers, so first we need to get the waveforms in there. There are several ways to do this:

Push from RB (Results Browser): Select a signal name (only one), RMB->Calculator
Pull from RB: Select the Wave button in the Calculator, then click on signal name in RB (use Family button to grab parametric sweep data)
Push from Graph: Select a trace (only one), Calculator icon
Pull from Graph: Select the Wave button in the Calculator, then click on the trace in the graph window (use Family button to grab parametric sweep data)
Pull from Schematic (ADE mode): Select appropriate signal type on the Schematic Selection toolbar in the Calculator (vt, idc, etc), then click on the net or terminal in the schematic. This is probably the most common way of using the Calculator and certainly the most intuitive.

Repeated pushing/pulling of signals into the Calculator will cause previously selected signals to be--you guessed it--pushed onto the stack. So now that you've got all your signals of interest in the Calculator, it's time to take a look at how to work with the buffer and the stack.

Buffer & Stack

First, make sure you can see the stack (View->Show Stack). Now take a second and hover your mouse over all the icons on the toolbars just above and to the left of the stack area. These icons are your best friends in working with the buffer and the stack. My personal favorite is the "Undo" button. No pressure. If you make a mistake, just click "undo'.

Another useful button is the one on the left labeled "Pick selected item and put into buffer". No popping it to the top of the stack, just "put this thing up there now". Use those 2 buttons and the occasional Push (green arrow) and Pop and there's no expression you can't build.

Functions

The simplest and most powerful feature of the Calculator is the wide selection of built-in functions available for operating on your waveforms. Setting the cyclic pulldown on the function panel at the bottom of the Calculator to All will display a long list of over a hundred functions for your use. Just click on the one you need and it will either be immediately applied to the contents of the calculator buffer, or it will display a small form so you can fill in the appropriate arguments for the function.

You probably will only use a handful of these functions on a regular basis, so why not RMB on the ones you use most often and select Favorites to add it to your Favorites list. Now you can use the cyclic pulldown to display only that reduced list of functions so you don't have to hunt around every time you use them.

Memories

There are plenty of times when you'll end up with expressions that a extremely long, wrapping through several lines in the buffer. Not only can this be pretty unwieldy to work with, but since you went to a lot of work to create those calculations, you'd love to be able to reuse them later. That's what you can do with Memories. Simply click on the "M+" button just under the buffer to store whatever is in the buffer as a memory expression. Use the "ME" icon or select "Memories" in the cyclic pulldown above the Functions area to display all your saved memory expressions.

The memory expressions can be saved to a file, where it might be easier to edit them. They can also be read back in from a saved file and sent back to the buffer.

Stacy Whiteman

Things You Didn't Know About The Rhinovirus and ViVA (Part 3)

2009-11-17T14:00:00Z

Okay, so I really have no idea how to tie those 2 things together, but I ran across this little widget the other day and just had to share it (slide the slider until it's about 2/3 of the way across). I know we've all seen electron microscope images of those transistors we're fiddling with, but do you really have any idea how small they are? Maybe you do, but I don't think I realized that the length of the gate of that transistor you're about to put in your circuit is the same size as a single rhinovirus (that's the common cold to use layfolks). Looks like you could fit a whole inverter inside of an influenza virus (would that make it not an influenza virus?). All I can say is...wow...and don't sneeze on my chip...

Okay, now on to our main topic--the ViVA Results Browser and a few useful features you may not have known were there.

Results Browser (RB)

The RB can be invoked from lots of places--from the Tools menu of the ADE L window or any ViVA graph window, from an icon in an ADE XL window, even from the CIW. And of course, the RB is your main base of operations if you invoke ViVA stand-alone. Once you've found it, click on the little icon that looks like a file folder to find a waveform database and open it. Go ahead, open more than one at a time. That's one of the real powers of the RB.

Searching through the hierarchy and through multiple databases

The bottom half of the RB has 2 tabs. If you click on the Search tab, you can enter a search string and find all the signals throughout the hierarchy in all open databases matching that string. Then you can select (or Ctrl-select) what you're interested in click the right mouse button and plot them. This is a quick way to compare the same signal from multiple simulations or to find a signal buried deep in the hierarchy.

Sweep Range

One way of sorting through the clutter of a large database, especially the results of a parametric sweep is to use the "Select Sweep Data" feature. This can be accessed by clicking on the icon at the top of the RB that looks like a set of horizontal lines with a curly bracket next to them (or from the Options->Select Data... menu item). If you have a parametric sweep database, you can then selectively highlight just the parameter values for the data you want to plot and instead of getting a whole family of curves, you'll only get the ones you want. If you've just got a single sweep database (like a regular transient run, for example), this features comes in handy to load only a limited slice of a large database. Just enter the start and end times in the form (use scientific notation for this--for some reason suffix notation doesn't work) and only that section of the waveform will be loaded and plotted.

Y vs. Y

Another feature of the RB that is fairly cryptic to use is the Y vs. Y plot. If you want to plot 2 signals against each other, here's how to do it. First click on the signal you want to be on the Y axis. Then click on the Y vs. Y icon at the top of the RB (looks like one Y with another Y lying down next to it). Finally click on the signal you want to be on the X axis and voila! the plot appears. Just remember, Y, then X.

Export

Finally, I wanted to point out some of the powerful data export features in ViVA. A waveform or trace can be exported from the RB (File->Export... or RMB->Export...) or from the graph window (select trace, then Trace->Save... or RMB->Save...). One popular application of this is to save the waveform in Spectre format so it can be used as stimulus in a Spectre PWL source. You also have to option to sample and/or interpolate the data to get specific step sizes.

Another useful application is to save one or more waveforms (or time slices of the waveforms) to PSF or SST2 format in order to reduce the size of the database. Data can also be saved in Matlab or CSV format for additional post-processing.

Happy browsing until next time...

Stacy Whiteman

Things You Didn't Know About Virtuoso: ViVA (Part 2)

2009-11-04T14:00:00Z

This week's installment, boys and girls, is brought to you by the letters H, V, m & a and by the symbol %. Apologies to anyone out there who didn't grow up with Big Bird and Cookie Monster. (Is that even possible?)

Remember those letters, we'll get back to them in a bit...

First a couple of FAQ's about axes in ViVA.

How can I tell which axis a signal is associated to?

Well, this isn't the easiest thing in the world, but if you look very closely, you'll notice one or more colored bars next to each axis title. They only appear if you actually have more than one axis on your graph, which will happen if you plot quantities of different units (like voltage and current). If you look closely, you'll see that the colored bars on each axis correspond to the colors of the plotted signals associated with that axis.

How can I move a signal from one axis to another (or to a new axis)?

This is easy. Simply select the signal you want to move by clicking on the waveform or it's name in the legend (don't forget you can use the Alt key--one of the sponsors of last week's episode--to quickly see which signal is which). Then, from the menu, select Trace->Assign To Axis and either select the axis you want to move it to or choose New Axis to do just that.

Now a word from our sponsors...

The letters H, V, m & a are the bindkeys you use to create interactive marker measurements in ViVA.

H (that's capital H, or Shift-H) will place a horizontal marker and Shift-V will--no fair, you peeked--place a vertical marker.
m (that's little m, without the Shift) will place a single point marker.
a (again, lowercase) will create a delta marker between itself and the most recent "m" marker.

There are several nice things about these markers.

You can have as many of them on your graph as you like.

You can select Marker->Show Table to get a tabular readout of all your marker intercepts with your signals. There's also an icon to do this. I'll let you find that on your own. If you move the markers (or rerun the simulation), simply press the Update icon in the marker table to refresh the values. This table can then be saved to a file for documentation.

They stay where you put them (unless, of course, you drag them to move them somewhere else--or delete them)

Speaking of dragging, you can drag the marker labels around to position them wherever looks nicest, without disconnecting the marker from the trace.

Speaking of marker labels, that's where our final sponsor comes in, the mysterious % symbol. First, double-click on the marker label to bring up the marker attributes form. The marker labels can be customized and the % sign is used to create some powerful types of formatting. The complete list can be found in the Virtuoso Visualization & Analysis Tool User Guide, but here are a few useful examples:
- %X, %Y will display the X and Y coordinates (%x, %y will display the 2nd X and Y coordinates for delta markers)
- %W, %H will display delta X and delta Y
- %N will print the name of the trace (handy on a crowded graph)
- My personal favorite, %E, works with the Expression field in the form to allow you to pull an expression from the calculator buffer or one of the calculator memories (more on that in a future episode) and annotate it directly onto the graph. This way you can get a clear visual representation of what is being measured. (Note: This was broken for a while, so make sure you've got the latest IC6.1.3 ISR if it doesn't work for you)

Now you can use the File->Save As Image or File->Print menu to save your beautiful graph to display at your design review.

Stacy Whiteman

Things You Wish You'd Thought Of...But You're Glad Someone Did!

2009-11-03T14:00:00Z

On Tuesday this week we are celebrating "Innovation Day" here at Cadence, honoring inventive engineers across the company.

I must admit that most of the time I get so bogged down with the latest customer questions or figuring out how to help people learn about the latest features that I forget about all those folks in R&D whose raison d'etre is to come up with new and better ways of doing things. And there are plenty of them. Sometimes their efforts aren't really obvious to the end user (a new algorithm under the hood, or new ways of helping us develop and support the software), but they still make a big difference.

Innovation doesn't have to flashy. Maybe it's a small idea which could make a big impact. Maybe it turns out to be just too big. Maybe it's finding a new way to make people change their old behaviors.

Whatever the size or scope of the ideas, we need innovative thinkers at all levels in the world today to solve problems and make our lives better. I'm very glad Cadence has chosen to set aside a day to recognize our own very talented engineers.

Stacy Whtieman

Things You Didn't Know About Virtuoso: ViVA

2009-10-27T13:00:00Z

Sorry I've been missing from this space for so long. I've been busily working on a number of projects to try to help get the word out about all the features I have been (and will be) blogging about. I've also been becoming an expert on making video demos, some of which I'll try to feature here too. Ask your Cadence rep about the new VSE L/XL and ADE XL/GXL interactive Quick Start Guides. (If they don't know what you're talking about, have them contact me...)

The next tool I'd like to take up is ViVA and I thought I'd try using sort of a "Top 3" format and see how that works.

As I realized during a customer presentation earlier this week, the first "Thing You Didn't Know About" ViVA is:

1. What is this "ViVA" thing of which you speak?

Yes, indeed, it suddenly occurred to me that if you use ADE, you'd never know that the waveform viewer is now called "ViVA". Someone at Cadence spent all that time coming up with a cute acronym and no one even knows about it unless they run the tool stand-alone (the executable is "viva") or access the documentation (perish the thought...).

Anyway, ViVA stands for Virtuoso Visualization and Analysis Tool and it consists of the Graph Windows, Calculator and Results Browser you use to display waveforms and make measurements after you run your simulations. Pretty important tasks and, yes, I know, features that many, many people feel extraordinarily strongly about.

So allow me to try to point out some of the little things that just might help you feel enthusiastic about using ViVA.

2. I've got all these waveforms on top of each other. How do I sort out this pile of spaghetti?

Don't worry. There are a lot of easy ways to do this.

First, you'll want to start by figuring out which signal is which. Hold down the "Alt" key over each trace and you'll see the name of the waveform as well as the name of the database file it came from. This can be especially handy for parametric sweeps, when you want to find out which sweep value goes with each curve.

Now, one way to quickly straighten things out is to change to strip mode. (Strip mode is where each waveform is plotted in its own little strip, and all the strips share a common X-axis). To do this, click on the 4th icon from the left at the top of the window, called "Strip Chart Mode" (or choose Axis->Strips from the menu). Voila! Lots of skinny little graphs.

Another way to clean up the graph is to move waveforms to other windows or subwindows. You can do this by clicking on a trace to select (or hold Ctrl and click to select multiple traces). You'll know something is selected if it turns green. Then click on the 6th or 7th icon from the left at the top of the window to move the traces to a new subwindow or a new window. You can also use the Trace->New Graph menu to choose whether you want to do a copy or move operation.

Regardless of whether you are in strip mode or not, did you know that you can drag traces around and drop them in other places to move them? You can rearrange strips in strip chart mode (drop the waveform in between 2 other strips), or you can drag one or more traces between subwindows or windows.

Did you know that Ctrl-X, Ctrl-C and Ctrl-V also work to cut, copy and paste respectively, just like in many other applications?

3. Is there a way to see where the actual simulation timepoints are?

Of course there is. (I wouldn't be writing about it if the answer was "no", now would I?). Just double-click on the trace to bring up the Trace Attributes form. Now, at the end of the line that says "Symbols", click the "Show" checkbox. Then, in the drop-down box next to it, select "All Points" and click OK. This can sometimes help you understand why the waveforms look the way they do.

Worth 1000 words

As they say, watching this in action might help you more than reading about, so please watch this short video showing these and other features in action. Also, click here for another video describing how to change the default colors for waveform plotting from ADE.

If the video fails to play click here.

Stacy Whiteman

Things You Didn't Know About Virtuoso ADE

2009-09-10T13:00:00Z

After delving into lots of new features in the Virtuoso Schematic Editor, the Library Manager and the Help System, I'd like to turn to our old friend ADE (aka Analog Design Environment, or for those of us who've been around awhile, Analog Artist). ADE is another one of those tools that you're probably using exactly the same way you've always used it because--well, because that's the way you've always used it. And besides Cadence hasn't done anything new to ADE in years...or have they?

Take a look at the ADE window on your desktop. I'll bet it's rectangular in shape about 700 pixels wide by 450 pixels high. Got it right, didn't I? Well, of course, because everyone knows that if you resize the ADE window, all you get is a bunch of extra blank space. Guess what, give it a try. We've now figured out how to resize the window properly so the contents expand to fill the extra area. The first time I showed that in a demo you could just feel the excitement in the room. All right, maybe not excitement exactly, but I did hear someone utter an only-slightly-cynical "wow".

So, besides this minor miracle, what other features have we added?

Edit in Place

Well, for starters, you'll notice that you can edit a lot of things in your simulation setup directly from the main window without having go through the menus and open a separate form. If you want to change the value of a design variable, just select the name and click in the value field to edit it. No need to do Variables->Edit..., select the name, type the number, click the Change button, then OK the form. That's about half the number of mouse clicks.

You can also check and uncheck the "Plot" and "Save" checkboxes directly from the main window.

For those items which can't be edited directly in the main window, things are simplified somewhat in that you can double-click on each entry and it will open the correct form entry for that item. For example, if you double-click on an output expression or an analysis, the form will come up with the settings for that particular entry.

VAR Parameterization

One really cool "hidden" new capability of ADE is that you can now create and use design variables just about anywhere in your simulation setup. This is done using what we call VAR syntax. For example, you can specify the transient analysis stop time by putting VAR("stopTime") in the appropriate field in the Choosing Analyses form. This will automatically create a design variable which you can change directly from the main window (and use in other places as well). Similarly, you can parameterize model files and sections, simulator options and many other things. More information on this useful feature can be found here.

Plot Refresh

You may also notice a new cyclic pulldown at the bottom of the ADE window, just under the Outputs section. It's labeled "Plot After Simulation" and the choices are "Auto", "Refresh" and "None". This allows you to control the behavior of your ViVA graph windows when you re-run a simulation. In the past, if you chose to auto-plot waveforms, any modifications you made to your graph windows were wiped out when you re-ran the simulation. If you had customized the graph at all, you had to turn off auto-plotting and then manually refresh each graph window after simulation to maintain your customizations.

Now you can select "Refresh" from this new pulldown and your graph windows will refresh with the new simulation data without undoing any modifications you may have made.

Something for the more adventurous user...

A really nice way to back-annotate results from parametric sweeps can be enabled by typing: artEnableAnnotationBalloon(t) in the CIW. This activates a large "balloon" when you hover your mouse over an instance. The balloon contains your specified annotation information for the different sweeps of the parametric run. More information on this can be found in the Virtuoso Analog Design Environment L User Guide under "Annotating Parametric Sweep Results" and a helpful video demonstration can be found here.

Well, that's all for now. Starting next time...Things You Didn't Know About ViVA!

Stacy

Things You Didn't Know About Virtuoso: RTFM

2009-08-25T13:00:00Z

Wait, don't run away! In this case I really mean "Read The Fantastic Manual". A recent comment by a reader prompted a spirited internal discussion here at Cadence regarding our Help system. I suddenly realized it had been ages since I even looked at it. Seriously, when was the last time you clicked on that "Help" menu at the top of your screen?

So I started doing some exploring and discovered that--what do you know?--there are some pretty interesting and useful things lurking under that menu!

Now I'm not trying to say all our manuals are "fantastic" or that you'll always get exactly the information you want in the blink of an eye. No help system is perfect. Face it, that little Microsoft paper clip guy thinks he can read my mind, but half the time I feel like twisting him into an ornament hanger to see if that wipes the smug little smile off his face.

Anyway, let's take a peek at what's been happening with the Cadence Help system while we weren't looking. First of all, you don't have to navigate the entire documentation library in order to get help. The Help menu at the top of each window has an entry to let you open just the document applicable to that window. So Help->Contents in the ADE L window opens the Table of Contents for the ADE L User Guide. Better yet, there's a Help button at the bottom of most pop-up forms which opens the relevant documentation for that form. And if you're using any of the IC 6.1 Assistants (as I keep reminding you to...), the "?" button in the upper right corner will give you the documentation for that assistant, many even with a link to a video demonstration showing you how to use it.

Really, I'm not kidding. Try it.

Each document has Find/Search field at the top and an icon which allows you to view/save that manual as a PDF file which you can print or browse in your copious free time on the platform of your choice. The Help menus also have entries to take you directly to Sourcelink or to the online Cadence Community Forums, where you can ask questions and interact with other users and helpful Cadence experts.

Now, I realize that everyone's user environment is different and you may not be able to access all these features (e.g. availability of internet access on Linux servers, etc.), but you should at least be able to access the manuals via the Help menus as I described. If you can't, you should contact your CAD folks and tell them you need "Help".

Until next time,

Stacy

P.S. I apologize that in my recent post, one of the webinars I pointed you to (Webinar 310: ViVA), had difficulties in the recording. We are working on an alternative delivery mechanism.

We Interrupt Your Regularly Scheduled Programming...

2009-08-10T13:00:00Z

I thought I would have time for a regular TYDKAV (Things You Didn't Know About Virtuoso) article this week before I go on vacation, but you know how it is when you're trying to get out of the office for a week. Things just seem to pile up higher than usual.

So in place of the usual witty repartee and pithy comments, I'll leave you with some pointers to some of the Virtuoso webinars that have been posted on Sourcelink recently. They've called these the 300-series webinars, a college course numbering analogy to let you know that you'll be getting a bit more technical depth and fewer colorful marketing slides...

Webinar 302: Minding the Gaps in Design Team Communication

This presentation explores the Virtuoso unified constraint system. It discusses the usage of electrical and physical constraints in the front-to-back design flow and illustrates how the Constraint Manager and Circuit Prospector Assistants help improve communication between circuit design and layout.

Webinar 310: Visualization and analysis of analog and mixed signal waveforms with the Cadence Virtuoso Platform

This multimedia presentation covers the ViVA waveform viewer and includes information on the new PSF XL waveform database format, details on how to customize your graphs, make interactive measurements and build expressions in the ViVA Calculator for use in ADE L and ADE XL.

Webinar 311: Specification driven design, analysis and verification with the Cadence Virtuoso Platform

This multimedia presentation provides a "quick-start" demonstration of the ADE XL tools, including how to setup multiple testbenches, define specifications and run sweeps and corners analyses in a single integrated environment.

All these webinars (and more) are available here and are each just under an hour in length.

I'll be back in a week or so with more TYDKAV as we begin to venture into ADE L, ViVA and ADE XL with a few side trips along the way.

Stacy Whiteman

Things You Didn't Know About Virtuoso: Customizing the Library Manager

2009-07-28T13:05:00Z

I've told you in previous postings about some new features in Virtuoso IC6.1 which make it quick and easy to open cellviews you use frequently--namely the recently-opened files list (found in the CIW->File menu) and the ability to bookmark one or more cellviews (File->Bookmarks->Add Bookmark from any cellview window).

While these features mean that you can open that cell you work on every day with just a couple of mouse clicks and minimal mental exertion, there will always be a time when you need to go up in the attic and find the box with the Christmas lights. Next year for sure you're going to remember to label that darn box before you put it away...

As usual, I digress. I'm talking about the Library Manager. I know you're all accustomed to using the Library Manager every day (shame on you if you haven't yet tried either of the 2 features mentioned above...). You probably haven't noticed that there are 47 libraries listed there. 17 of them don't exist any more. 15 of them don't apply to your project at all. 7 of them are reference libraries which you don't have edit rights to. The other 8 are scattered all over the list. Why should you have to strain your already-overworked brain cells sorting through that mess? And what happens if you forgot that one of those libraries was just an experiment you tried once and forgot to delete when that version of the block never worked correctly? What happens if you pick that one as the basis for your new design instead of the one that worked? I don't know about you, but I've got enough gray hairs already...

So I wanted to point out 2 new features of the Library Manager which might help you streamline the way you view all that data.

Look at the Pretty Colors...

The first is the ability to customize the display attributes of any library. For example, you can specify that your reference libraries be shown in red text with a particular icon and your design libraries be shown in green text with a different icon. You can even hide some libraries so they don't get in your way, but are still accessible to the software. (Maybe you want to show your "experimental" libraries in a different color too...)

Basically the way you do this is to edit your cds.lib file. Somewhere after the DEFINE statement for a library, put the line:

ASSIGN <libName> DISPLAY <displayName>

where <displayName> is the name you're going to give to a particular set of display attributes (we'll get to that shortly).

Now when you open the Library Manager, select Edit->Display Settings. In that form, you'll be able to select your <displayName>(s) and change their colors, icons and other attributes.

All Together Now...

The 2nd new feature for library display is the ability to create "combined" libraries. Maybe you want to display all the reference libraries for your project under a single name in case you forget which cell is in which library. Don't worry, the libraries aren't physically combined, just displayed that way.

To do this, first you'll need to create a dummy directory with the name you want to give your combined library (kind of a kludge, but oh well). Then edit your cds.lib and add 2 lines:

DEFINE <combinedLibName> <pathToDummyDirectoryYouCreatedAbove>

ASSIGN <combinedLibName> COMBINE <lib1> <lib2> ...

These lines need to go after all the lib1, lib2, etc. libraries are defined.

That's it. Now when you open the Library Manager, you'll see your combined library name with a "+" sign next to it. If you click on the combined library name, you'll see all the cells in all the libraries combined. If you click the "+" sign, you can still access the libraries individually as usual.

You Do Know About Categories, Don't You?

BTW, if you look at the screenshot above, you also notice that each of my libraries has categories defined within it so I can further refine my cell selection by block or by celltype. That feature has existed in Virtuoso for years now and hopefully you're already making use of it (Hint: check out Edit->Categories from the Library Manager)

I'm running out of time right now, but you can read more about all these features in the Cadence Library Manager User Guide.

Until next time...

Stacy Whiteman