Tutorial - The Five-Minute Schematic
tutorial is entitled "The Five-Minute Schematic and
Simulation" and will give you a taste of how quickly you can put
together a circuit with full simulation. These tutorials are intended
only to introduce you to LogicWorks features. For complete details on
any subject, see the reference manual that comes with LogicWorks.
In the following tutorial sections text with a square,
step-by-step instructions for achieving a specific goal. Other text
provides background and explanation of the actions being taken.
Start the :LogicWorks program by double-clicking on its icon.
Once the program has started, you will be looking at a screen like this:
circuit window is your view port onto the circuit diagram, which you
manipulate using the various drawing tools. The smaller panel at the
bottom of the screen will be used by the program to display a timing
diagram of the signals in your circuit, as well as other outputs
generated by your circuit. Either of these windows can be moved or
resized by the usual methods to suit your needs.
Placing a Device
Parts Palette shows a merged list of all parts in all open libraries.
Libraries can be opened and closed manually by using the Parts Palette
pop-up menu's Open and Close commands, or any collections of libraries
can be opened automatically at start-up by placing them in the Libs
directory. The Parts Palette appears as follows:
list of open libraries can be changed manually by doing either of the
collection of libraries can be opened automatically at start-up by
modifying the INI file. The procedure is described in more detail in
the LogicWorks Reference manual provided in electronic form with the
- Click on the File Menu and select the Libraries submenu;
then choose the New Lib or Open Lib commands as needed.
- Right-click on the Parts Palette , and use the same set of
library commands that appears in that menu.
The numbered devices in this library
are generic 7400-series types. The labeling and simulation
characteristics can be adjusted to match the various 7400 families on
- Locate the Filter text box on the Parts
Palette. Type the text 164 into this box. This step will reduce the
parts list to only items containing that text.
- Locate the part 74_164 in the parts list, and double-click
the cursor back into the circuit window. The cursor on the screen will
now be replaced by a moving image of the selected symbol, in this case
an 8-bit shift register.
- Position this image somewhere near the
centre of the circuit windows , and click the left mouse button. A
permanent image of the device will now stay behind in that location,
and the cursor image will continue to follow the movement of the mouse:
More devices of the same type could be created at this point, but in
this example we wish to select another symbol:
the spacebar to return to Point mode. Notice that you can click and
drag the device that you placed to any desired new position.
again to the Parts Palette, and this time double-click on the XNOR-2
type. (You might need to change the text in the "Filter box, if you
used it in a previous step). Once you move outside of the Parts
Palette, the cursor will immediately change to match the new symbol.
XNOR-2 and the devices in the Simulation Gates, Simulation Logic, and
Simulation I/O libraries are called primitive types because they have
built-in simulation models in LogicWorks. Other devices such as those
the 7400 library, are called subcircuit types , because their
simulation models are made up of primitives. If LogicWorks is being
used only for schematic entry, it is also possible to make symbols with
no simulation function.
- Place one of the Exclusive-NOR
gates adjacent to the 164 device so that the pins just touch., and
click once to anchor the device.
- Press the spacebar to return to Point mode.
you place devices or signal lines so that they touch, you will notice
that the signal lines flash briefly. This indicates that a logical
connection has been made. You do not need to explicitly request a
Moving a Device
at the Exclusive NOR gate, and click and drag to the right. While you
hold the left mouse button, you can drag the device to any desired new
position. Note that any signal lines attached to the device are
continuously to maintain connection.
- Position the gate to the right of the 164 device so that it
appears as follows:
a connection to the output of the gate by positioning the pointer near
the endpoint of the pin and dragging away to the upper left
- Notice that two lines at right angles will follow your
mouse movements to connect the starting and ending points.
While moving the mouse, try pressing the CNTRL or ALT key, and note the
different line-routing methods available. Click the left mouse button
once to anchor th signal line. For details on these line-routing
modifier keys, see the section on signal-line editing in the LogicWorks
reference manual provided in electronic form with this software.
- Leave a right-angle line attached to the gate as follows:
- Extend this line to connect to the B input of the 164 by
clicking at the line endpoint where you left off, dragging the line to
the B input, and releasing the mouse button:
- Add a connection to pin A by clicking at the end of the
pin, dragging the line down until it touches the signal line, and then
releasing the mouse button:
Notice that an intersection dot appears automatically whenever three or
more lines intersect.
- Try repositioning a line segment by clicking and dragging
anywhere along the length of the segment except at a corner or
- Return to the Parts Palette and select a Binary Switch
- Place it as shown on the following diagram.
- Press the spacebar to return to Point mode.
- Try clicking on the switch. Notice that it changes between
the 0 and 1 states.
In order to move a switch, you must first select it by holding the
SHIFT key while clicking on it. This is necessary because the switch
has a special response to a normal mouse click.
The devices in the Simulation I/O library can be used to actively
control and observe the simulation right on the schematic. Each of
these devices responds immediately to changes in the simulation in
progress. The Hex Keyboard device is similar to the switch except that
it operates on four lines at once.
- Select a Clock device and place it on the diagram just
below the switch.
- Press the spacebar to return to Point Mode
- Route wires from the switch and clock to the 164, as shown
in the following diagram(remember to try using the CTRL and ALT keys to
route the wires):
While you have been working on the diagram, the LogicWorks
simulator has been running continuously, simulating the effects of the
new connections that are being made. So far, though, we have not asked
it to display any results. This is done either by placing probes on the
diagram or by displaying signals in the Timing window.
Naming a Signal
- Click on the text tool in the Tool Palette. The cursor will
then change to a pencil shape, which will be used to select the item we
want to name.
The text cursor is used to name devices and signals, to apply pin
numbers to device pins, and to add free-text notations to the diagram.
- Position the tip of the pencil anywhere along the length of
the line running from the clock device, and click. A blinking insertion
marker will appear:
- Type the name CLK on the keyboard and then press the ENTER
key or click the left mouse button once outside the text box.
You will immediately see the Timing window come
to life, with the displayed values on the CLK line:
- Return to Point mode by clicking the arrow icon in the
Tool Palette. Note that the name can be dragged to any desired
- Click once on the Binary Switch to change it to the logical
By default, any named signal is shown automatically in the Timing
window, although you can change this setting by using the Add
Automatically command in the Simulation menu.
- Again using the text cursor, name the two data lines from
the shift register and the output line from the gate as follows:
The simulated output from
these lines will immediately appear in the Timing Window.
Click on the <> and >< buttons, and observe
that they affect the timing scale of the Timing window.
The display resolution can be adjusted over a wide range of time values
to suit the displayed data.
- Select the Timing Window item in the View menu. You will
notice that the Timing window disappears and the current time indicator
in the Simulation palette advances much more quickly.
- Select the Timing Window command again or use the
button to reenable the display
- Click on the Reset() button, and notice that
the simulation restarts at time 0.
- Adjust the speed slider control
in the Simulator toolbar, and notice the simulation slows.
- Click repeatedly on the Step () button, and observe that
the simulation proceeds one step at a time.
- Click on the Run button in the
button advances the simulation to the next time at which there is some
circuit activity, not necessarily just one time unit. The size of the
step will depend upon the circuit.
- Select the Binary Probe type from the Parts Palette.
- Place a probe so that its pin contacts a signal line to
view the simulation value on that line:
the simulation progresses, the values on all probes are updated
immediately. A similar device, the Hex Display, is also available to
show groups of lines in hexadecimal. These simulation devices can be
flagged to indicate that they are not a real part of the finished
product and should not be included in any netlists or bills of
- Click in the window, but away from any circuit objects.
This deselects everything.
- Click on the XNOR gate to select it.
- Select the simulation Params command in the Simulation menu.
- Use the controls in this box to increase the propagation
delay in the device to 5 ns:
The Simulation Params command is used to view and set delays associated
with devices and pins. Pin delays normally default to zero, but can be
used to fine-tune the delays for different paths through a device.
Device Delay on
the Timing Window
that the altered device delay immediately affects the simulation. You
will see an increased delay between the clock reference lines and the
changes in the FEEDBCK signal:
Interacting with the Simulation
- Try clicking on the switch hooked to the CLR input:
Notice that it changes state and immediately affects the displayed
Save the Design
Click the Save button(
save your circuit so you can continue with it later.
This ends the Five-Minute Schematic and Simulation tutorial section.
The next tutorial is Schematic