SUE Tutorial Version 4.1

SUE Tutorial 4.1

SUE Features

• Draw, view, and edit schematics, ICONs, random graphics and text.
• Built in netlister to Verilog, HSPICE, Berkeley SPICE, and IRSIM.
• Cross probe directly with Verilog, IRSIM, HSPICE, and MAX (MMI's custom layout editor).
• Interactively run Verilog and IRSIM, with logic values displayed directly on the schematic.
• Automatically attach documentation, Verilog models, etc. to schematics.
• Automatic version control.

This tutorial will carefully walk you through these features and many more.

Getting Started

Before we get started make sure someone has already installed SUE at your site.

INFO:   To run some parts of the tutorial you will need to have programs like HSPICE, Verilog, and IRSIM (IRSIM switch level simulator is included with MMI-SUE). If you do not have one or more of these simulators, simply skip that section and go on to the next.

Starting Up SUE

Before starting up SUE, make a new directory. Go to that new directory and type:

cp -r $MMI_TOOLS/tutorials/sue .

Don't forget the "."

cd sue

Typing "echo $MMI_TOOLS" will tell you where the MMI tools are installed. The directory you just copied contains files that you will need to run the tutorial.

Then to start SUE type:

sue

A window should come up that looks something like this:

SUE Screen Layout

On the very top of the window the title bar should say:

SUE: no_name S <path_to_cell> (spice)

"no_name" means that you have not specified the file (schematic) you wish to edit. The "S" means that you are editing a "Schematic", as opposed to an ICON.

Also, in parenthesis, you'll see spice displayed. This means that you are currently in spice simulation mode.

Next across the top you should see the menu bar which contains the following menu items: File, Edit, View, Sim and Help.

These are pull down menus much like any Mac, or PC application.

Directly to the right of the Help menu is the "SUE Info Bar". It currently says "Welcome to Micro Magic SUE (MMI_SUE4.1.5)". Note that the 4.1.5(or what ever the number is) refers to the version of SUE you are running.

Icon Library List Boxes

Down the right side of the window are several small Library List boxes.

The top one is the Schematic List Box. This lists all current schematics that have been loaded into SUE. Currently only no_name should be listed.

The next box is the Icon List Box. This Icon Library List box typically displays all of the Icons SUE has loaded for your current schematic. It should be blank for now.

The next two (sometimes only one) Library List Boxes are typically used to display the Icons for various library elements. These are sometimes referred to as "Lib List" boxes in this document. In this example the mspice and devices libraries are shown.

Scroll bars are shown across the bottom and right side of SUE (and are found in the List boxes). These work like the scroll bars in most other applications.

The Help Menu

• Hold down the left mouse button (Button- 1) and drag the cursor over to Help menu and then release the left mouse button. This will bring up the Help Menu which contains the complete on-line SUE manual. It also contains "about SUE", the "MMI documentation guide" about all MMI tools and software in distribution, the SUE FAQ, bug reporting and this tutorial!

 
In addition to providing detailed information on all of SUE's commands, modes, and features, the SUE manual explains the philosophy behind SUE. After finishing this tutorial you should read through the manual. In fact, it would be very useful to read the sections on SUE Philosophy and Selection at this time.

TIP!    Going back to the Help menu, when you hold down the left mouse button (Button-1) over the Help menu, notice that there is a dotted line just before the "about SUE" menu item (not shown in the above figure).

If you release the button while over the dotted line the menu will "tear off". The menu then works like any other Xwindow (window manager dependent). It iconifies by clicking the little triangle in the top left corner. You can move it by clicking and holding down the left mouse button (Button-1) over the top title bar and dragging it around (release button to stop). Or you can close the window by holding down the right mouse button (Button-3) over the top title bar and selecting Close from the menu that pops up.


 

TIP!    You can also just click on the Menu items and the pull down will stay down until you click on the desired item.

• For now close the Help menu.

Drawing A Schematic

OK, we are now ready to draw a schematic using SUE.

We are going to draw a very simple (and not very useful) circuit that simply generates a pulse. The circuit we are going to draw is:

Creating a New File

First we will name this file.

• Pull down the File menu and select new schematic . This will bring up the File Select box. Note that you could have also used the hot key Ctrl-n to bring up this menu as well. That is, hold down the Control key and then type n (while still holding down the control key).

INFO:   Many SUE menu items have "hot" key options for frequently used commands. This is to make your work go a lot faster as you get more familiar with SUE.

Once you have popped up the File Select box, a blinking cursor appears in the highlighted "Filename:" area (at the bottom of the dialog box).
• Now type in Pulse_generator, or any other name you like. You can then either hit return on your keyboard, or click the OK button in the window to put away the File Select box. You should now see Pulse_generator in the upper right Schematic List box, and in the title bar at the top of the window. The title bar tells you that you are editing "Pulse_generator".

Beginning the Schematic

Now to draw our schematic.

• Start by clicking the left mouse button (Button-1) over the inverter in the mspice Library List box. It's in one of the bottom boxes on the right hand side. If you don't see the inverter label use the scroll bars to move the list until you find it.

Be careful NOT to click the middle mouse button (Button-2) in the Library List box as it will bring up the ICON for editing.

• Once you have clicked on inverter, move the mouse over the large blank grey area in the middle of the window and click the left mouse button again. This "drops" the inverter ICON into your schematic.

 
Notice that an M has appeared to the left of the "Pulse_generator" name in the Schematic List box. This tells you that you have modified the current schematic.
If you tried to quit SUE it would first ask you if you wanted to save your changes. Go ahead, try it.
• Select Exit from the File menu. The Cells Modified dialog box will come up and tell you that you have modified cells.
• For now click Cancel since we don't want to exit.
• If you had clicked Exit, SUE would have quit without saving your schematics.

Selecting and Editing Objects

SUE lets you do lots of interesting things to the selected object. For example, let's take the inverter you just dropped and rotate it.
To do this make sure the inverter is selected. The inverter should be a different color, i.e. blue, if it is selected.
• If it is not selected simply move the cursor over the inverter, and as the cursor moves over the inverter it should turn white, meaning it is "active".
• Now click the left mouse button (Button-1) and the inverter should turn yellow.
• If you move the cursor off the inverter it will turn blue. Objects which are blue are the selected objects.
• To rotate the inverter simply hit r on your keyboard and the inverter will rotate 90' clockwise. Type r three (3) more times and it will be back to the start.

 
TIP!    You can also type u for "undo" to undo your last action. SUE gives you 100 levels of undo!

 
You can also move, flip, duplicate, and modify the inverter. All of these features and more are found under the Edit menu. Edit menu features work on the selected object or objects. Once again, you can use either use the menu or the handy hot keys.
OK, let's try another Edit option.
• Select the inverter and type d. This will make a duplicate copy.
• Now click and hold down the middle mouse button (Button-2). This changes you into "move" mode. While holding down the middle mouse button move the cursor; this should move the inverter. When it's where you want it simply release the mouse button. Place the duplicate inverter to the right of the first inverter.
• Make a third inverter (duplicate an inverter already in the schematic) and place it to the right of the first two.
• Now go back to the " mspice " Library List box and get a "nand2" and drop it to the right of the three inverters. Remember, you do this by clicking the left mouse button (Button-1) over the nand2 in the Lib List box, then moving the cursor to where you want to drop the device and clicking the left mouse button again. If you didn't place the nand2 exactly where you wanted it don't worry, simply click and hold the middle mouse button (Button-2) and move it just as you did with the inverter.
• We now need two more items from the Lib List boxes, pulse and global. Grab them and drop them to the left of everything else as in Figure 3.

 
The "pulse" ICON generates a pulse for SPICE.
You can change the properties of that pulse by simply double clicking the left mouse button (Button-1) on the pulse ICON. In fact, double clicking on any object allows you to change its properties.

For example, say we wanted the third inverter to be bigger, maybe an 8/4 (P=8, N=4).

• First, double click with the left mouse button (Button-1) on the inverter. This brings up the Edit Properties dialog box as in Figure 4.
• Simply change the WP box from 2 to 8, and the WN box from 1 to 4. (WP is the pfet width and WN the nfet width).
• Click Done, or hit return, and the inverter will magically be changed from a 2/1 to a 8/4.

The "global" ICON generates a global signal for programs like HSPICE and Verilog.
For our "Pulse_generator" we want the global to be ground to provide a reference for our pulse generator.
• Simply double click on the global ICON and then type gnd into the Edit Properties dialog box.
• Hit return or Done to close the dialog box and assign "gnd" to global signal.

 
Since you have done some work you should now save your circuit.
• Do this by selecting Save from the File menu, or type the hotkey Ctrl-s.

 

INFO:   Vdd and gnd will not only work for SPICE but will also generate the current levels (1 or 0) for IRSIM and Verilog.

Generators in SUE

Many of the sample gates provided with SUE are generators. A SUE generator takes arguments that can structurally change its icon and/or schematic (unlike parameterized icons) and creates a new icon/schematic. Hence, for every generator, a multitude of cells can be generated, depending on the combination of its arguments.
For example, the nand2 icon is actually a generator. You can edit the number of inputs and/or specify that you want to use a demorgan equivalent icon. The schematics under the icon will also change based on the number of inputs.
• Select the nand gate by clicking on it with the left mouse button.
• Push into the schematic (hotkey: e or from the View menu, select "push into".
• Look at the schematic.
• Pop back up to the Pulse_generator schematic (hotkey: ctrl-e or from the View menu, select "pop out of".
• To change the generator properties, hold down the shift key and double click on the nand gate with the left mouse button. The pop-up for in Figure 5 will appear.

• Change ninputs (number of inputs) to 3 and click on Done. Notice that the icon changes to have 3 inputs.
• Push into the icon again (hotkey:e) and notice that the underlying schematic has changed.
• Pop back up to the to the Pulse_generator schematic (hotkey: ctrl-e) and undo the change (hotkey: u). The nand gate should now have only 2 inputs.

Wiring Up the Circuit

We are now ready to wire up the circuit.

• Select add wire from the Edit menu or type a w on your keyboard. This puts you into "wiring" mode.
• Now move the cursor to the small square on the top of the "pulse" ICON. Click the left mouse button (Button-1) on top of the square. This starts a new wire at that point.
• Move the cursor up (vertically) away from the box. A wire should follow your cursor. When you get up to about the level of the inverter input port click the left mouse button again and move the cursor to the right. The mouse click should have created an anchor point which allows you to put a bend into the wire.
• When you get the mouse over the left (input) port of the inverter hit the middle mouse button (Button-2) to end the wire. If it is electrically connected the little "clear" box indicating the port of the inverter should turn into a small black filled box. If open boxes appear at the wire end and the inverter port, you missed. Don't worry, you can simply add another wire segment. SUE will even fix it up and make it look good for your boss :-)

TIP!    Oh, by the way: You might have noticed that SUE puts a white X at the nearest port to your wire. If you like that location then simply double click the left mouse button (Button-1) and SUE will wire it up for you.


 

• To wire the first two inverters, we'll use another method. Select the middle inverter (click on it with the left mouse button).
• Hold down the middle mouse button and move the middle inverter until the input port of the middle inverter overlaps the output port of the left inverter. See Figure 6.
• Release the middle mouse button.
• Now, hold down the middle mouse button again and move the middle inverter to the right. Notice that the inverters are wired up. You can use this method of wiring instances as you are placing or duplicating instances.

 
• Now wire up the other pieces as shown in Figure 3.

 

TIP!    If at anytime you are in a mode and something goes wrong, you can type Ctrl-c to abort that mode. For example, if your wire isn't going the way you want it to, typing Ctrl-c will abort that wire.


 

TIP!    You should notice that to the right of the Help menu in the menu bar the SUE Info bar will tell you what each item will do in that mode. In fact, the SUE Info bar gives you lots of help. As you run the mouse down the menu items in the menu bar, it tells you what each of them does. For example, click the left mouse button (Button-1) on Edit then run down the menu items. Notice that add text says "Add text into the current cell". Try it!


 

• Before going on to the next section save your schematic (hotkey: ctrl-s).

Running Simulators

Running HSPICE

If you don't have HSPICE installed, skip this section. If you do, let's go for it!
OK, pay close attention. To run HSPICE you have to do the following set of complex tasks:
• Type h
This simple looking "hot" key (found in the Sim menu under "spice it") actually does a lot.

 
First, it builds an HSPICE netlist.
It then runs a script to go out and find all machines with an HSPICE license and start your SPICE job on the one with the smallest load (assuming the script has been installed on your machine).

 
When your SPICE job is finished it loads up the output, and starts up New Spice Tool (NST). NST is a SPICE waveform viewer written by Micro Magic and is included with MMI-SUE.

TIP!    If you have two monitors on your machine and one of them is running SUE, you can have NST start up on the other monitor (see manual for details).

Plotting Your SPICE Output

Now you will start to see some of the real power of SUE.

• To see how your circuit simulated, simply select one of the wires in your schematic and then type p for plot. The waveform for that wire should show up in the NST window.

 

TIP!    There are lots of plotting options in the Sim menu such as "Plot and Remember", "Plot Old Node", "Unplot", etc.


 

INFO:   NST can do a lot more than just plot what it's given from SUE. For example, you can add panels (under the Panels menu), print out your waveforms, and even do arithmetic derivations! (See the NST manual for details).

You can even plot nodes at different levels in the hierarchy. In this circuit there are only two levels of hierarchy. The one we are looking at, and the transistor level circuit of the inverters and nand2. So, lets "push" into the nand2 gate and look at it more closely.
• To push into "nand2" simply select the nand2 ICON, and then type e for "edit". You can now select any node inside nand2 and plot it. Try it.
• To get back to the next higher level, or "pop", type Ctrl-e. This should take you back to "Pulse_generator".

 

TIP!    If you ever get lost and want to get back to a given schematic, just click the left mouse button (Button-1) on the schematic you wish to edit in the Schematic List box in the upper right.

Running IRSIM On Your Schematic

Ok, now for something really different. We are going to run IRSIM on your circuit. IRSIM is a switch level simulator from Stanford University. We have included it with SUE. In most other CAD tools you would have to draw a different schematic to run IRSIM, but not with SUE. SUE can run SPICE, IRSIM, and Verilog all from the same schematic!
At this point SUE thinks you want to SPICE things. Since we now want to run IRSIM we have to tell SUE, and its netlister, that we want to use the IRSIM simulator, and as such generate a ".sim" file.
• To do this select change simulation mode from the Sim menu. The Change Simulation Mode box should pop up.
• Click on "sim" for Netlist Type . Notice that Properties automatically updates.
• Click Done, or hit return.

 
Notice that SUE has removed the NST window. This is because NST is used for plotting SPICE waveforms. IRSIM comes with it's own waveform viewer/analyzer.
• To run IRSIM simply type the same hot key you used to run HSPICE, h

 
SUE will now build a sim netlist. You may notice that the inverter and nand2 transistor-level schematics "flash" at you for a split second. This is because sim is a flat netlist, as opposed to a hierarchical netlist.

INFO:   SUE keeps track of what you have done, and in the case of netlisting SUE keeps track of what has changed. Once files for HSPICE and Verilog have been generated, SUE "disk caches" them. The next time you need to netlist, SUE only updates the changes. Unfortunately, sim is an old format that does not support hierarchy, so SUE must re-netlist everything. The flashing is just to let you know SUE visited that cell.

SUE then takes the netlist, fires up IRSIM in interactive mode, and brings up the analyzer.

Interacting with IRSIM

IRSIM is now running in interactive mode. You are at "time 0ns", and nothing is set to anything (except power and ground). To begin with we must have an input. For SPICE we used the pulse ICON. This ICON only generates waveforms for SPICE. Since you most likely want to do something else in IRSIM (or Verilog), SUE ignores the SPICE pulse source and generates the appropriate netlist for IRSIM.
To "set" an input we must first select the node we want to drive.
• In this case, select the wire just on top of the pulse source. It's the one that goes into the input of the first inverter, and the nand2 gate.
• Then go to the Sim menu and chose irsim set low (hotkey: 0). This will tell IRSIM to set that node to a "logical 0".
• Since this is the only input to the circuit we can now "step time" forward.
• To do this choose irsim step, or simply type the "s" hot key.
• To plot that node type "p" as you did in SPICE mode. The timing waveform should appear in the analyzer window.

 
Let's look at another node.
• Select the nand2 output and type p. Notice that the nand2 output went high when the input went low.
• Now go back to the input and set it high by selecting it and typing 9 (or choose irsim set hi from the Sim menu). Step time again by typing s.
• Notice that the nand2 output went low, and then some time later back high. Yep, we actually have a pulse generator.

 

Netlisting And Node Names

When we plotted a node in the analyzer window, you might have noticed that a name appeared on the left side of the waveform. That is the name that SUE gave to the node when netlisting it.

You could have given it a name yourself by dropping a name_net_s, from the "devices" Lib List box, on the wire and editing its properties, but since you didn't SUE made one up. The other way a net gets assigned a name is if you have attached a port to the net (see the next section).

TIP!    Because it may be difficult to select the small name_net icon, first place a name_net_s icon in an open area in your schematic. Double click with button-1 on it and name it. Once it has been named, move it onto the desired net.

When you select a wire, SUE will show the name of that wire in the Menu Message box. In this case it will be something like "net_1". This feature is quite useful when running HSPICE.

INFO:   HSPICE only recognizes 14-character names, and allows only certain characters. SUE, on the other hand, will let you name a node almost anything you want. If you happened to name a node something that HSPICE won't accept, SUE will automatically convert that name into something HSPICE can handle.

Higher Level Schematics

Verilog

We have already simulated our little pulse generator in IRSIM and in HSPICE. Now we want to run a Verilog simulation. Unfortunately, you can't simply set nodes in Verilog like you can in IRSIM. You need to have a test file to drive them. To accomplish this we will first make an ICON for our cell, and then wire our ICON up to a clock generator that has been provided for you.

Adding Ports

Before we make our ICON we need to add some I/O ports to our circuit. We are going to place and name them as shown in Figure 7.

• To attach the I/O ports, start by getting an input from the Lib List box and attach it to the wire above the pulse. Remember, click with the left mouse button (Button-1) to grab or drop an ICON, then use the middle mouse button (Button-2) to select and move it.
• Next grab an output and attach it to the output of the nand2. Since we would like to look at more than one output, duplicate the output port (select, then d) and wire it up to the output of the third inverter.

• To "name" the I/O ports double click on the input port to call up the Edit Properties dialog box.
• Type in into the name box, then click Done or hit return.

 
For the outputs we will use a little trick that allows us to name multiple signals. It's not much for only two ports, but when you have 32 wires it helps a lot.

Naming Multiple Signals

• Select both of the ports. You can do this by clicking the left mouse button on one of the ports and shift clicking (hold down the shift button while clicking with the left mouse button on the second port) on the other port. Or you can simply hold down the left mouse button (Button-1) and drag the selection box around both ICONs. Make sure to select ONLY the two output ports.
• Go to the Edit menu and select name objects. The "Name Selected" dialog box (see Figure 8) will appear. Type out in the "name_prefix" box. Type _H for "name_suffix". Change the direction from north (n) to south, s. When you are finished click Done or hit return.
• Save your circuit (hotkey: ctrl-s).

Making An ICON For Our Circuit

We are now ready to create an ICON for the Pulse_generator.

• To make an ICON, select make other view from the View menu (or type Shift-c). This creates an ICON for "Pulse_generator" and will bring you to that ICON. It should look like Figure 9.

Notice that SUE has placed the ports for you.

The "+" is the origin of the ICON. It is used for placement, rotation, etc. The text lines saying "-type user -name name/M/DPC" are user properties that will appear in the Edit Properties dialog box if you do an "edit properties" (double click with the left mouse button) for this cell.

Now we want to draw a representation of what we expect our Pulse_generator ICON to look like when we place it into another schematic. For this example, we will just draw a box with some text in it. We are going to make our ICON look like Figure 10.

Drawing the ICON

Start by drawing a box. You can make a box out of multiple lines, or use a rectangle. Both actually generate the same thing in the SUE database.
• To draw a box using lines, select add line/rect from the Edit menu. Click with the left mouse button (Button-1) to start your line, and with the middle mouse button (Button-2) to end it. You can move the line using the middle mouse button.
• To draw a rectangle, select add line/rect from the Edit menu, then click and hold down the middle mouse button (Button-2), and draw out the area you want for your rectangle. If you missed, don't worry. You can move the rectangle just like any other object in SUE (middle mouse button).

 
Notice the instructions which appear in the SUE Status box (to the right of the Help menu) when you begin to draw.
• You can resize your rectangle by clicking and holding down the left mouse button (Button-1) on one of the squares in the corners of your rectangle, then dragging it to where you want the vertex to be.

 

INFO:   If you need to resize the rectangle later, double click with the left mouse button on the rectangle and the squares will appear.

Adding Text

Let's add some text to our cell. First, we will type in the name of the cell, so we know what the cell is when placing the ICON.

• To do this select add text from the Edit menu, or use the hot key t, and click the left mouse button (Button-1) where you want the text to start. This puts you in text mode. Notice that directions are provided in the SUE Status box to the right of the Help menu.
• Now simply type in Pulse_generator and hit return.

 

TIP!    You can also increase or decrease the size of the text. Double click with the left mouse button (Button-1) to select the text and put you into text mode where you can edit or add text. If you then hit Shift-right mouse button (Shift-Button-3) the text will get larger. Shift-left button (Button-1) makes it smaller, and Shift-middle (Button-2) reverts to the original size.

The ports that SUE has placed for you will show up as small dots when the ICON is placed into a schematic. To help identify the ports, we should add some text so we know exactly what those ports are. SUE has a built-in option to help you with this.
• Start by selecting the " in " port.
• Select duplicate text from the Edit menu. This will give you the text "in", which WILL show up in the ICON view. Move the "in" text inside the box next to the "in" I/O port.
• Now select both of the output ports together and generate text for both of them using the Shift-t hot key (duplicate text). Place the "out" text inside the box as shown in Figure 10.

 
One last item. We want to personalize our cell, so let's add a new property:
• To do this select the -type user -name M line and duplicate it ( d hotkey and then button-2 to move it). This is just to save some typing.
• Double click on the copy to enter the edit text mode. In the text replace the M with

my_name -default Bob

Somewhere inside or near your ICON type the new text line:

I'm $my_name

INFO:   You can use the arrow keys or the pointing finger to move the cursor to the place where you want to enter text. Use the Delete or Back Space keys to delete text.

What you have just done is to create a new user property, set its default to "Bob", and displayed it in your ICON.
• Now type a c (" swap views " in the View menu) to get back to the schematic.

 

Placing our ICON into the schematic

Let's see what our ICON looks like. To do this, we are going to place our ICON into our schematic.

Don't worry, SUE is smart enough to know it's the ICON for this schematic and to avoid recursive calls when netlisting.

• To place your Pulse_generator ICON into the Pulse_generator schematic, simply go to the ICON List box at the right side and click with the left mouse button (Button-1) to select then place an instance of the new Pulse_generator , as you would any other ICON. Your schematic should now look like Figure 11.

Modifying the ICON

Just in case your name isn't Bob (yes, I know there are lots of you) let's change the name in the ICON.

• Double click on the ICON and change "Bob" to your name in the Edit Properties dialog box.

 
The ICON should now say I'm " your name ". Notice that SUE automatically added the property "my_name" and the default "Bob" to the Edit Properties dialog box.

And finally, let's add a title box to our schematic.

• Select title_bar from the Lib List box and place it at the bottom of your schematic. SUE automatically puts your schematic under version control (highly recommended) as soon as you save your file.

 
Your schematic should now look like Figure 12.

INFO:   Actually, SUE always puts your schematic under SCCS control. The Title Bar simply gives you information about the state of the schematic.


 

• Save your schematic.

Using our Pulse_Generator

• Open the file clock.sue (select open from the File menu). This is just to load a clock generator.
• Start a new schematic by choosing new schematic in the File menu. Call it " Test_pg ". It is going to look like Figure 13.

Place a copy of Pulse_generator.

• Use the left mouse button (Button-1) to grab the Pulse_generator from the Icon List box and drop it into the schematic.
• Then place a copy of clock .
• Wire them up.

 
Now let's attach a couple of "flags" to the output of "Clock", and the Pulse_generator outputs.
• Grab a flag from the Lib List box and drop it on to the Clock output. Duplicate the flag twice (hot key d ) and wire them onto the Pulse_generator outputs (refer to Figure 13 if needed). The flag on "out1_H" has been rotated for easier viewing.

You Are Now Ready to Simulate Your Circuit

• Go up to the Sim menu and change simulation mode to " verilog " in the Change Simulation Mode dialog box.
• Now select verilog netlist from the Sim menu. This builds a Verilog netlist using our Pulse_generator and a behavioral model of "Clock" (which has been provided).
• Select init probe from the Sim menu. This starts up an interactive Verilog simulation.
• Type s for "step time". This sends several cryptic lines to your Verilog simulator, which causes it to advance the time step 1 unit. A "0" should appear in the flag nearest "Clock", and a couple of "1'"s on the output flags.
• Step time a few more times.

 
The clock is set up to step every other time step. Notice that the out0_H flag changes every cycle with the clock, and is the inverse of the clock. This makes sense since it is just the clock followed by three inverters. But what happened to our pulse on " out1_H "?
Well, it turns out that we used a transistor-level Verilog netlist of the Pulse_generator. While HSPICE and IRSIM know how long it takes transistors to switch, Verilog doesn't. What's happening is that the inverters are taking no time (i.e. 0ns), so in Verilog our "pulse" lasts for 0ns! To fix this we will add a behavioral model for the inverters in Pulse_generator.

 

Creating Behavioral Verilog Models And Attaching Them To ICONs

• Push into the Pulse_generator (hotkey: e ).
• Now select and push into the inverter .

 
We are going to create a Verilog model for our inverter which has a non-zero delay. Since the library inverter you just pushed into cannot be modified, you will need to make your own version to modify.
• To make your own inverter go to the File menu and select copy .
• When the dialog box comes up type my_inverter into the filename box and hit the return key. This will make an exact copy of the inverter cell along with its ICON.
• Save "my_inverter" (hotkey: Ctrl-s ).
• Now type c , which will switch you to the ICON view of "my_inverter".
• To identify "my_inverter" from the library inverter hit the t hot-key or select add text from the Edit menu.
• Click the left mouse button (Button-1) somewhere near the inverter symbol and type my_inverter , then hit return. This will display the words "my_inverter" on the ICON view whenever you typed it.
• Edit the verilog property to add a delay. In the following line add the #4 as shown (see Figure 14).

-type fixed -name verilog -text {assign #4
 $out = !($in)\;}

INFO:   The Verilog property text you just edited tells the netlister how to netlist this cell if there is a behavioral Verilog model for this cell. The port names will automatically be placed into the behavioral file.

• Type c again to get back to the inverter schematic.
• Now type Ctrl-e to get back to the "Pulse_generator" schematic, or click with the left mouse button (Button-1) on the Schematic List box.

 
Next you will need to replace the library version of the inverter with your new inverter, "my_inverter" in the "Pulse_generator" schematic. To do this go back to Pulse_generator.
• Click the left mouse button (Button-1) on Pulse_generator in the Schematic List Box . Remember, it's the topmost file box. This should bring up the Pulse_generator circuit.
• Next, click the left mouse button (Button-1) on my_inverter in the ICON list box (the second file box) and place a copy of "my_inverter" into the "Pulse_generator" schematic. Just don't drop it on top of anything else.

 
Now you get to use a cute little feature in SUE, replace instance.
• To replace the library inverter with "my_inverter", simply select one instance of the lib inverter using the left mouse button (Button-1).
• Then type the b hotkey (" replace instance " from the Edit menu). Now move the mouse over "my_inverter" and once again hit the left mouse button (Button-1).

 
If all went well, the lib inverter should have been replaced with "my_inverter".
• Now replace the other two instances of the lib inverters with "my_inverter". When you have done this, remove the extra copy of "my_inverter" that you first dropped into the schematic. Remember - you remove objects by first selecting them and then typing the q hotkey.
• Save "Pulse_generator"

 
Now let's get back to our pulse generator test circuit, "Test_pg", and simulate it.
• Click the left mouse button (Button-1) on Test_pg in the Schematic List Box to return to the Test_pg schematic.
• Select verilog netlist from the Sim menu as you did before. Then do an init probe ( Ctrl-i ).
• Step time ( s ) a few times and see what happens.

 
You should see that out0_H follows in, but with a one cycle delay. Also, now out1_H generates our pulse!

Creating a More Complex Verilog Model

For the inverter in the above example, the Verilog model could be described in a single line. If you need to write a more complex Verilog model, you can attach a behavioral Verilog file to a schematic. We'll use the Pulse_generator from the above example.

• Click the left mouse button (Button-1) on Pulse_generator in the Schematic List Box to return to the Pulse_generator schematic.
• Select edit verilog from the Sim menu, or use the hot key shift-e . A dialog box will come up telling you that it can't find a Verilog file for Pulse_generator. Simply hit the Done button and SUE will make one for you, and then bring up the file in your text editor (EMACS, VI, etc.).

 
Your text editor file will look like Figure 15.

Notice the SUE automatically creates a template for the behavioral model automatically adding the port information to the file. You would add the behavioral model for Pulse_generator after the line:

// Enter verilog here

• Save the file and close the text editor window. If your editor is EMACS (the default), type Ctrl-x, Ctrl-s to save, followed by Ctrl-c to exit or in VI type :wq to save the file.

 
SUE keeps track of your behavioral Verilog file and "attaches" it to your schematic. You can view/edit it any time by simply selecting edit verilog from the Sim menu as you did before. Since the file exists now, SUE will bring it up for you automatically. You can do this either from the schematic, or by selecting the ICON in a higher level schematic.

INFO:   Notice SUE has named your behavioral Verilog file "Pulse_generator.vb" (note the "b"). If you want to write and attach your own behavioral Verilog files, they must have the ".vb" extension. Otherwise, SUE won't find them. SUE uses other extensions to tell it what the files are for as well. These include:

.vg : Gate-level flat Verilog from dpc mode in SUE
.vh : Gate-level hierarchical Verilog from SUE
.vb : Behavioral Verilog (used by "Edit Verilog" in SUE)
.vi : Verilog include file for .vh files
.h : HSPICE header include file
.v : Normal user-written Verilog RTL file (not used by SUE except to import port information)
 

Higher Level Simulations

You have:

Drawn a schematic.

Simulated it in HSPICE

Simulated it in IRSIM

Simulated it in Verilog

Created ICONs, behavioral Verilog models, etc.

You see that you can do a lot with SUE.

A More Complex Example

Now let's look at something a little more complex.

• Open the file Demo_ripple_4_bus.sue., which should look like Figure 16.

 
This example is a 4-bit ripple counter, but you can read that in the text. Notice also that the text says there is a document attached to this schematic.
You can bring up the document (but don't do it yet!) by selecting display cell doc from the View menu. Once you do this, SUE will display the doc in your browser. If your browser isn't running SUE will start it; however, if it is running SUE will load the doc (.html) file. Since you may be looking at this tutorial in your browser, note that the adder document will be loaded over the tutorial and you will have to come back to the tutorial.

 

INFO:   You can also attach plain text files, in place of HTML files. SUE looks for the ".html" or ".doc" extensions to files with the same names as the schematic you are editing. It brings up ".html" files in your browser, and ".doc" files in your text editor.

TIP!    You can choose the default for your docs to be in either HTML or text in your .suerc file. You can also choose your text editor and browser in your .suerc file as well. See the SUE manual for more details.

Feel free to look over the adder example. It has documentation, buses, and lots of other interesting things not covered in your simple Pulse_generator.

TIP!    SUE is smart enough to remember where you just were. Let's say you just pushed down five levels and you want to pop back up four levels. To accomplish this just repeat Ctrl-e four times. To push back down type e four times.

Displaying Design Hierarchy, And Controlling What Gets Simulated

One of the more powerful features in SUE is that it can change what you simulate on the fly. The display design hierarchy feature allows you to not only display the hierarchy, but to control what level of the design gets simulated.

To control what gets Verilog simulated, SUE uses two types of files. Those with the ".vh" extension are hierarchical Verilog files which SUE creates automatically for you. Files with a ".vb" extension are "behavioral" Verilog files, which are hand written by you.

SUE and Verilog Netlisting

When SUE builds a Verilog netlist (".vh" file) it starts from the cell you are currently in (the root cell) and looks for all of the subcells and wires connecting them together. SUE then looks at each subcell to see if there is a behavioral model for that cell (".vb").

If a ".vb" file exists (behavioral model) and if you told the netlister to use the behavioral model (via the display design hierarchy menu item) SUE will simply insert the ".vb" model for that subcell.

If no ".vb" file existed, or if you told the netlister to push down further, SUE will push down into each subcell where it does the same netlisting operation of looking at subcells and wires connecting them, while continuously building up a netlist.

If you do not tell SUE to use any behavioral models, SUE will follow down each subcell all the way to the Lib devices (i.e. nmos, pmos, inverters, etc.).

Now let's look at an example of how you can control what you simulate using SUE.

• If you aren't already there, go to the Demo_ripple_4_bus schematic. Enter the Verilog simulation mode ( change simulation mode to verilog ).
• Generate a Verilog netlist by selecting verilog netlist from the Sim menu.
• Now select display design hierarchy from the Sim menu. The Design Hierarchy dialog box should pop up on top of your schematic and look like Figure 17.

 
When you netlisted, SUE created the Verilog file Demo_ripple_4_bus.vh from the schematic. This is a Verilog text file and you can view it in your favorite text editor. You can also run Verilog on this file.
• Now, click on the line that says - I ripple_4_bus .
• Click on the netlist button.

 
The " - I " changed into a " > S ", and another line " - I FA " has appeared underneath and slightly indented.

Now look at the file Demo_ripple_4_bus.vh again. Notice it has changed. What has happened is that there was a .vb file for ripple_4_bus. The "-I" told you that SUE was going to netlist with that .vb file (associated with the ICON for that schematic).

When you clicked on the ICON line SUE expanded down a level to the FA ICONs, thus displaying -I FA. At the same time SUE generated a new Demo_ripple_4_bus.vh file.

• If you now click on the -I FA line and then click on the netlist button, you should see the devices contained in the FA cell (see Figure 18). Likewise the Demo_ripple_4_bus.vh file will be updated.

 
By changing the display design hierarchy in SUE, the designer or verification person can change what is being simulated on the fly. Thus schematics can be "flattened" to verify that they are correct down to the "transistor" level, or simulations can be done at very high-level behavioral levels to increase speed.
In addition, mixed level simulations can also be done. That is, simulate high-level behavioral models for some blocks, and flatten others down to the transistor level.

Most importantly, what you see in the display design hierarchy window is what you get when you simulate. You never have to wonder what you are actually simulating!
 

TIP!    One VERY helpful debugging option is the
display term values

 (hot key Ctrl-o) in the Sim menu.

Try running Verilog on the adder example.
• Select verilog netlist (hotkey: shift-n ) from the Sim menu then init probe (hotkey: ctrl-i ).
• Step for a few cycles ( s ) and you should see the flags update.
• Push down into ripple_4_bus and type Ctrl-o . SUE will display all of the current simulation values at that level.
• At any time you can choose display term values (Ctrl-o) and SUE will display the current value of all of the terminals on the schematic you are looking at.

 

INFO:   Remember that display design hierarchy has determined what you actually simulate. If you had set display design hierarchy to use a behavioral model for ripple_4_bus, then while running your Verilog simulation, if you push down into ripple_4_bus and try to display term values (hot key Ctrl-o) NO values will be displayed.


 

This is because you told your Verilog simulator to use a behavioral model for ripple_4_bus, and as such it did NOT receive any information below the ripple_4_bus level. So remember, display term values (hot key Ctrl-o) can only display the logical values that have been generated by the Verilog simulator and the Verilog simulator only simulates what you have given it via display design hierarchy


.

When you are done looking over the adder example go to the next section.

Cross Probing With MAX

If you purchased MAX (also from Micro Magic Inc.) along with SUE, you can do what is called "cross probing" between SUE and MAX. Both SUE and MAX have complete tcl/tk interfaces. This means that you can write and execute full tcl programs in either tool. Tcl also provides a means for inter-program communication. SUE and MAX use this notion of "send" commands to talk to each other. Cross-probing is one example of this inter-program communication.

• If you don't have SUE running at this time, start it, and load the FA cell. If you are continuing from before, click on the FA cell in the Schematic List box. Your screen should look like Figure 19.

• Change simulation mode to " sim "
• Select max cross probe init from the Sim menu.

If MAX was running it will load the ".max" file for FA. If not, SUE will start up an xterm window, and then launch MAX from there. MAX will come up with the FA layout.
A sim netlist is then created from the MAX layout and LVS (Gemini LVS is provided with the MAX software) is run to compare the schematic and layout. The nets which match are highlighted in SUE in blue and highlighted in MAX in the highlight layer.

Select a wire in SUE (click on it with button-1) as shown in Figure 20 and type k (max cross probe in the Sim menu) . The wire that you selected will be highlighted on the layout in the MAX window as shown in Figure 21.

• You can also select a net in MAX by clicking on it with the left mouse button.
• Then select " SUE crossprobe net " (hotkey: k) from the MAX Misc menu. The corresponding net will be highlighted in SUE.

MAX is a very powerful, full custom layout editor with a complete language and API. Refer to the MAX Manual and MAX Tutorial (accessed from the Help menu) for more details.