Creating and Simulating a Schematic with Design Architect and Quicksim

1. What you will learn

1.1 How to create a schematic for a design using Design Architect.
1.2 How to name nets, name components, and modify properties on the schematic.
1.3 How to simulate the schematic using Quicksim II.

2. Getting started

2.1 This tutorial and those that follow it assume you are familiar with the Unix environment and commands within it to create directories, list, copy, and move files, etc. Knowledge of a text editor available on Unix systems like vi or xemacs is also required. If you are not familiar with Unix, it is recommended that you obtain the relevant take-outs from University Computing Services on these subjects and study them or see the Basic Introduction to Unix available on-line.

2.2 First, you should create a separate directory under your home directory to hold the designs for this tutorial:

>> mkdir tutorial

>> cd tutorial

2.3 Start the Mentor Graphics Design Architect (DA) tool (the ampersand [&] puts the tool in the background so your prompt comes back and you can use that terminal for other commands):

>> da &

You will see a number of statements printed out in the window where you started DA . This is normal. All of the Mentor tools print out the commands that you have executed into the window from which the tool was run from (called the transcript window). This feature is useful in seeing what you have just done, and also is useful for capturing commands to create a script file, as you will do later in this tutorial.

You should see a printout in the transcript window somewhat (but not exactly!) like the one below:

// analog_da (ANALOG/DA Personality Module) v8.5_2.2
// bpl_da (Board Process Library Personality Module) v8.5_2.1 Wed Jun 19 15:15:54 SST 1996
// esi_da (ESI/DA Personality Module) v8.5_2.7
// quickhdl_da (QuickHDL/DA Personality Module) v8.5_5.2
// srp_da (SRP/DA Personality Module) v8.7_1.1 Mon Feb 3 18:42:03 PST 1997
// syn_blocks_da (AutoLogic BLOCKS/DA Personality Module) v8.5_2.1
// vhdlwrite_da (VHDLwrite/DA Personality Module) v8.5_2.4
// Design Architect v8.5_2.14 Fri Feb 14 15:45:06 PST 1997
// EDDM v8.5_2.14 Mon Feb 17 16:28:39 PST 1997
// Falcon Framework v8.5_2.6 Wed Jan 22 13:41:10 PST 1997
//
// Copyright (c) Mentor Graphics Corporation, 1982-1995, All Rights Reserved.
// UNPUBLISHED, LICENSED SOFTWARE.
// CONFIDENTIAL AND PROPRIETARY INFORMATION WHICH IS THE
// PROPERTY OF MENTOR GRAPHICS CORPORATION OR ITS LICENSORS.
//
// Mentor Graphics software executing under Sun SPARC Solaris.
//
// Warning: Environment variable override for: $SCMOS_IC_TECH (from: DDMS/DDMS_Core/DDMS_FILE 82)
// Note: Default ripper symbol pathname for auto-ripper instantiation set to $MGC_GENLIB/rip/1X1 (from: Capture/gdc/note 98)
// Note: Executing /idea.B4/pkgs/quickhdl_da/userware/default/da_session.dofile (from: Capture/gdc/note 99)
// Note: Executing /idea.B4/pkgs/srp_da/userware/default/da_session.dofile (from: Capture/gdc/note 99)
// Note: Executing /idea.B4/pkgs/syn_blocks_da/userware/default/da_session.dofile (from: Capture/gdc/note 99)
// Note: Executing /idea.B4/pkgs/vhdlwrite_da/userware/default/da_session.dofile (from: Capture/gdc/note 99)
// Note: PLDSynthesis II install (from: Uims/base_toolkit/ui_session_tk 81)

You should also see a new DA window like the one shown below appear on the screen:

2.4 Open a new schematic sheet. Like all of the Mentor tools, DA usually gives you several ways to perform each command. You can open a new schematic sheet by either clicking the  button on the session_palette on the right side of the DA window with the left mouse button, or using the File->Open->Sheet... menu item from the pull-down menus at the top of the window. Either way, the Open Sheet dialog box, like the one shown below, should appear:

Note that the current Unix directory where the tool was started (called the working directory) is printed in the Component Name box. Now you need to add the name of the new schematic you want to open (create) to the end of this directory name. Click the left mouse button in the right part of the component Name box and type:

/and_gate

Another thing you should note about typing in dialog boxes in the Mentor tools is that the Delete key on your keyboard will delete all of the highlighted text in the currently active box (the one with the red box surrounding it), and that the Backspace key will remove the character to the left of the cursor - be careful when using the Delete key!

The Open Sheet dialog box should now look like the one below:
 
 

Click on the OK button in the Open Sheet dialog box. A new schematic window should appear in the DA window as shown below:

Note that along with the appearance of the schematic window, the session_palette was replaced with the schematic_add_route palette (usually called the schematic palette). This palette will be used to construct the schematic by adding wires, busses, etc.

3. Add a component to the schematic

3.1 Add an AND gate to the schematic. There are numerous libraries of parts available with the Mentor tools and within DA as well. This includes the standard 7400 series TTL parts, CMOS parts, high speed parts, and parts for specific programmable logic and ASIC families. However, for this tutorial, you will use the simple generic parts supplied with DA, called the gen_lib parts.

Use the Libraries->MGC Digital Libraries->Display Libraries Palette item from the pull down menus at the top of the window to bring up the MGC Digital Libraries palette in the right hand side of the window as shown below.
 
 

Click on the gen_lib item to bring up the gen_lib palette. You will see the list of components available within the gen_lib library. You can scroll up and down through the list by placing the cursor in the gen_lib palette window and pressing the Page Up and Page Down keys.

Scroll to the top of the list and select the and2 component. This will add the and2 component to the active symbol window, bring up the Place Part dialog box at the bottom of the DA window, and when the cursor is place in the schematic window, a ghost image of the component will appear:
 
 

Place the cursor in the middle of the schematic window and press the left mouse button to place the component on the sheet. A single instance of the and2 component will be placed on the sheet and the Place Part dialog box will disappear. Note that the and2 component will remain in the active symbol box. If another instance of the and2 component is desired, you can click on the active symbol box with the left mouse button and the Place Part dialog box will come up and another and2 component can be placed as before.

3.2 Practice moving the component to another location. Now that the and2 component has been placed in the schematic, it is still "selected" which means that any of the commands such as move, copy, delete, etc. will apply to it. A component, wire, or property on a schematic that is selected will appear highlighted in the its color will be changed to white and the lines will be dashed. Many of the commands for manipulating objects on a schematic are available from pop-up menus in the schematic window. These pop-up windows are context sensitive in that they have different commands available within them depending which type of part (or parts) on the schematic are selected. The context that the pop-up menu applies to will be indicated by the title at the top of the pop-up menu, Instance in this case.
With the and2 component still highlighted, place the cursor in the schematic window and press the right mouse button. The pop-up menu shown below should appear (note that only the schematic window is shown below):
 
 

With the right mouse button still pressed, slide the cursor down until the Move menu item is selected in the pop-up menu. Release the right mouse button. The Move dialog box will appear at the bottom of the screen and a ghost image of the component will appear and follow the cursor within the schematic window. Move the cursor to another location and press the left mouse button to move the and2 component.

3.3 Unselect the and2 component. Place the cursor in the schematic window and press the right mouse button to bring up the pop-up menu again. Slide the cursor down to the Unselect menu item and release the right mouse button. Notice that the and2 component is now unselected:

4. Add wires to the schematic

4.1 Add wires to the inputs and outputs of the AND gate. Bring up the schematic palette by placing the cursor in the gen_lib palette and pressing the right mouse button to display the Schematic Palette pop-up menu. Select the Display Schematic Palette menu item and the gen_lib palette will be replaced by the schematic_add_route palette. You could have also done this by selecting the Libraries->Display Schematic Palette item from the pull down menus at the top of the DA window.
In the schematic_add_route palette, click on the  button. This will bring up the Add Wire dialog box at the bottom of the DA window and change the cursor to a cross hair that snaps to grid locations on the schematic window. Place the cursor on the output pin of the and2 component (the small purple diamond) and single click the left mouse button. Move the cursor two grid spaces to the right and single click again. Move the cursor down one grid location and double click the mouse button to end the wire. Notice that a single click of the mouse button adds a "vertex" or pivot point, to an active wire, and double clicking ends the current wire. Also notice that when a correct connection has been made to the pin of a component on the schematic, the purple triangle disappears.

Add wires to the inputs of the and2 component in a similar manner:

Click on the Cancel button in the Add Wire dialog box to remove it and use the pop-up menu in the schematic window to Unselect the wires. Notice that the pop-up menu was titled Net when the wires were selected (context sensitive, remember?)

4.2 Add names to the nets. Naming nets in a schematic is very helpful during simulation as the net names will be displayed as the names you have added to them, which makes them easier to track down. You can add names to a net by selecting the entire net and adding them, in which case the names will appear on each vertex, or you can add them to a single vertex only. In each case, the net is named in the schematic database the same way, the only difference is the fact that the name appears in different places.

Select the net on the and2 component's output by using the pop-up menu in the schematic window to select the Select Area->Net: item. Draw a box around the net on the output (or any part of it) and it will be selected. Use the pop-up menu again to choose the Name Net menu item. The Add Property dialog box with the Property Name set to Net will appear. Put the cursor in the Property Value box and type out1 . Click the OK button in the Add Property dialog box. A ghost image of the out1 net name will appear in the schematic window and follow the cursor. Place the cursor above the appropriate wire and click the left mouse button to place the net name.

To name the first input to the and2 component, place the cursor exactly on top of the end of the wire (the vertex) and click the left mouse button to select it. A cross symbol should appear on the vertex indicating it was selected. Use the pop-up menu to select the Name Nets: menu item again. (Note that if the pop-up menu comes up with the ADD title and without the Name Nets: item, the context isn't right suggesting that you haven't selected the vertex correctly) Type in in1 as the Property Value in the Add Property dialog box and place the name above the appropriate wire. Add the name in2 to the other input to the and2 component in a similar fashion.

Use the View->All item from the pull-down menus at the top of the DA window to center the component in the window and zoom in:
 
 

5. Add an instance name to the and2 component on the schematic

Each specific occurrence of a component on a sheet is called an instance. Like nets, DA will add default names to instances, but if you add your own instance names to each component, tracing values during simulation will be easier.

5.1 Select the and2 component by using the pop-up menu in the schematic window to select the Select Area->Instance menu item. Draw a box around any portion of the and2 component and it will be selected (you could have also selected it by clicking on it directly with the left mouse button - some items can be selected directly like this).

5.2 With the and2 component selected, use the pop-up menu (context sensitive to the Instance title now) to select the Properties->Add->Add Single Property menu item. The Add Property dialog box shown below will appear:
 
 

Select the INST item in the Existing Property Name box, and type gate1 into the Property Value box. Click the OK button (without changing any of the other items in the dialog box.

An Add Property dialog box will appear at the bottom of the DA window and a ghost image of the gate1 property will appear in the schematic window and follow the cursor. Place the gate1 property below the and2 component by moving the cursor to the proper location and pressing the left mouse button.
 
 

6. Modify the rise time and fall time properties of the and2 component

Most components in the Mentor libraries have timing value properties on them so that you can add real timing parameters to the simulation of your design. The gen_lib components have rise time and fall time parameters. The default values for these properties is 0 as can be seen on the schematic. Now you will change these properties to some non-0 value to add timing information to the schematic.

6.1 Change the value for the rise time property. Once a property appears on the schematic, the best way to modify it is to first select it. Use the pop-up menu in the schematic window to select the Select Area->Property menu item. Draw a box around the top `0' below the and2 component which will select it. Now use the pop-up menu again (context sensitive to Property/Text now) the select the Change Values: menu item. The C hange Property Value dialog box will appear in the bottom of the DA window. Change the value of 0 in the New Value box and click the OK button in the dialog box. The number should change from 0 to 10 on the schematic.

6.2 Change the value for the fall time property. There is a short cut to changing the value of a property on a schematic. Place the cursor exactly over the bottom 0 property on the schematic under the and2 component and press the <shift> and <F7> function keys simultaneously. The Change Property Value dialog box will appear as before and you can change the contents of New Value box from 0 to 6 and click the OK button.

Use the pop-up menu in the schematic window to choose the Unselect menu item to unselect the property. The schematic should now look like the one below:
 
 

7. Check and Save the schematic sheet

Before a schematic can be saved in DA , it must be checked for errors. This ensures that the sheet has been constructed correctly and can be simulated.

7.1 Use the Check->Sheet menu item at the top of the DA window to check the sheet. A Check Sheet transcript window like the one shown below should appear.
 
 

There should be no warnings or errors on your schematic sheet1. In general, schematics that have warnings will still simulate, but the warnings generally indicate that there is a potential problem, so you should check them out. Obviously, any errors must be corrected before the sheet is saved.

The errors and warnings in the Check Sheet transcript window are hyper-linked to the schematic to help you locate problems. For example, if CheckSheet had reported an error or warning on net N$1, you could click on the "N$1" entry in the transcript window and the corresponding net would be selected (and thus highlighted) in the schematic.

Once you are finished looking at the Check Sheet transcript window, you can close it by clicking on the upper left hand corner and selecting the Close menu item, just as you would for any other Unix window.

7.2 Use the File->Save Sheet item from the menu at the top of the DA window to save the sheet. Close the schematic window and DA window as you did above or by using the MGC->Exit menu item. Your AND gate schematic is now ready to simulate.
 
 

8. Use the QuickSim II tool to simulate the and_gate schematic

8.1 The QuickSim II tool is the simulator for designs that are produced by Design Architect . You invoke the tool from the command line on the specific sheet you want to simulate like this:

>> quicksim -tim typ and_gate &

The QuickSim II session window shown below should appear.

The -tim typ command line option tells the Quicksim simulator that you want to add the timing information you modified in the schematic to the simulation, i.e., 10 ns rise time and 6 ns fall time. If you omit this option, the design will still simulate the same, but the timing information you added to the schematic will not be used. In this case, the rise time and fall time (the gate delay) will be set at the default value of 0.1 ns. Simulating a design without gate delays is sometimes useful in simulating the function of a design only. Omitting the timing information from the simulation means that you don't have to worry as much about figuring out how long it will take the outputs of the design to reach their final values before you change one of the inputs, like figuring out how long the clock period should be, for example.

8.2 Use the  button to open the schematic sheet. This allows you to select actual signals on the sheet to add traces, force them to values, etc. The QuickSim window should now look like this:

8.3 Add traces to the simulation to display the state of the signals in the design. Now that the sheet window is displayed, you can select signals in the window by clicking on them. Click on the in1 , in2 , and out1 signals to select them (they will highlight in the sheet window). Like DA , QuickSim has context sensitive pop-up menus. Use the right menu in the session window to bring up the pop-up menu and use the Add ->Traces->Selected menu item to add a traces window to the session with the selected signals displayed. Your QuickSim window should now appear like this:

8.4 Add forces to the inputs of the design. Forces are the mechanism used in Quicksim to drive values on signal lines at specified times in the simulation. In general, you should be careful to only add forces to the inputs to a design you are simulating. Adding forces to the outputs of a design can override the values that the circuit is trying to produce which can lead you to believe that the circuit is not functioning correctly when in fact, it might be.

Use the Unselect->All item in pop-up menu to unselect all of the signals. Reselect the in1 signal by clicking on it in the schematic window. Use the Add->Forces->Multiple Values... item in the pop-up menus to bring up the Force Multiple Values dialog box. Fill out the dialog box as shown below and click OK .
 
 

Note that when you do this, the following commands are printed in the transcript window:
 
 
$force("/in1", "0", 0, void, void, @relative, @norepeat, void);
$force("/in1", "1", 20, void, void, @relative, @norepeat, void);
$force("/in1", "0", 80, void, void, @relative, @norepeat, void);
These commands can be captured in a text file (using cut and paste from the transcript window into another X window with a text editor running) and used to build a script or do file to rerun the simulation with the same test vectors, if necessary. This is a very useful way to run repeated simulations when debugging a complex design. Creating and using a do file will be explained in more detail in the next section.

Select the in2 signal, and using the Add->Forces->Multiple Values... item in the pop-up menu, add a force to the in2 input with the following value-time pairs: 0 - 0 ns, 1 - 20 ns, 0 - 40 ns, 1 - 60 ns, 0 - 100 ns.

8.5 Run the simulation for 120 ns by using the Run->Simulation->For Time... item from the pull down menus at the top of the Quicksim window and typing 120 in the resulting dialog box and clicking OK .

Make the trace window active by clicking on top of it and use the View->All item from the pull down menus at the top of the Quicksim window to expand the traces out to the full size of the window. The Quicksim window should look like the one below.
 
 

8.6 Use cursors to measure the rise and fall times of the AND gate output. With the trace window still active, use the pop-up menu within it to select the Cursors->Add... menu item. Type test1 in the Cursor Name field of the Add Cursor dialog box that comes up and change the Time field to 20 and click OK . Add additional cursors called test2 at time 30, test3 at time 40, and test4 at time 50.

Use the View->Area: item from the pull down menus at the top of the Quicksim window to bring up the View Area dialog box. Draw a box around the time period from about 10 ns to about 60 ns. Be sure to include all of the signals (make the box go from the top to the bottom of the trace window). The trace window should now look something like this:
 
 

Note that below each cursor there are two times shown. The top one is the location of the cursor in absolute simulation time, and the bottom one is the time relative to the first cursor. Using the cursors as they are, we can read the rise time as the time between the test1 and test2 cursors - 10 ns, as we would expect, given the values we added for the property on the schematic. For the fall time, the test4 cursor is not located on the falling edge of the out1 signal.

To move the test4 cursor, select it by clicking on top of it. When it is selected, it should change to a different color. Use the Cursors->Slide/Snap: item from the pop-up menu in the trace window to bring up the Slide/Snap Cursor dialog box. Use the down arrow button in the Mode field to change the mode to snap_to_nearest_edge . Click on the falling edge of the out1 signal, and the test4 cursor should snap to it as below. Click Cancel in the Slide/Snap Cursor dialog box to remove it.
 
 

Note that the fall time can now be read as the time between cursor test3 (40.0 ns) and test4 (46.0 ns), - 6 ns, again, as expected given the value for the property on the schematic.

8.7 Quit the Quicksim simulator by using the close item from its X window menu and selecting Without Saving and OK in the Exit QuickSim dialog box that comes up.
 
 

9. Use the QuickSim II tool to resimulate the and_gate schematic using a do file

As mentioned previously, a do file is a text file of commands (in the Mentor Graphics scripting language called AMPLE) that can be used to automate tasks like repetitive simulations for debugging purposes. The syntax of the AMPLE commands fore each action you want the tool to do can be looked up in the Mentor documentation, but a better approach is to simply execute the command once in the actual tool, and then capture the resulting command from the transcript window into the do file.

9.1 Using a text editor (such as xemacs), create a text file, called and_gate.do , that contains the following commands:
 
 

$$open_sheet(["/ : sheet1"], @noentity, @pop_existing);
$$add_traces(@nooverlay, void, void, @nomap, "", "in1");
$$add_traces(@nooverlay, void, void, @nomap, "", "in2");
$$add_traces(@nooverlay, void, void, @nomap, "", "out1");
$force("/in1", "0", 0, void, void, @relative, @norepeat, void);
$force("/in1", "1", 20, void, void, @relative, @norepeat, void);
$force("/in1", "0", 80, void, void, @relative, @norepeat, void);
$force("/in2", "0", 0, void, void, @relative, @norepeat, void);
$force("/in2", "1", 20, void, void, @relative, @norepeat, void);
$force("/in2", "0", 40, void, void, @relative, @norepeat, void);
$force("/in2", "1", 60, void, void, @relative, @norepeat, void);
$force("/in2", "0", 100, void, void, @relative, @norepeat, void);
$run(120, @relative);
$add_cursor("test1", 20);
$add_cursor("test2", 30);
$add_cursor("test3", 40);
$add_cursor("test4", 50);
$set_active_window("Trace");
$view_all();
Note that most of these commands should appear in the transcript window from the previous Quicksim session and can be cut and pasted from there.

9.2 Start the QuickSim tool on the and_gate design as before:
 
 

>> quicksim -tim typ and_gate &

The same Quicksim window should appear as did the previous time you started the simulator on this design.

9.3 Execute the and_gate.do file by placing the cursor inside the QuickSim session window and typing dofile and_gate.do . Note that as soon as you start typing, a grey session dialog box will appear containing the letters you are typing. Hit <CR> when you are finished typing. The session dialog box will disappear and the AMPLE commands in the do file will be executed. These AMPLE commands will open the and_gate schematic sheet, create a trace window with the appropriate signals in it, add the necessary forces, run the simulation, add the cursors, and finally, zoom out on the resulting traces. The result should be a Quicksim window like the one below.
 
 

You can now zoom in on the cursor area and move the test4 cursor as before to measure the fall time.

Print the Traces window:  Make sure the Traces window is selected.  Then choose File->Print->ActiveWindow from the top level menu.  A print dialog box will popup.  Enter mgcprint for the printer name and leave all other fields as defaults.  You must use "mgcprint" for the printer name in order to get the screen graphics to print correctly.  Your screen should look similar to the one below.  Select OK to print the Traces window.
 

 
9.4 Quit the Quicksim simulator by using the close item from its X window menu and selecting Without Saving and OK in the Exit QuickSim dialog box that comes up.