Jianjian Song LogicWorks 4 Tutorials (5/15/03) Page 4 of 14
Select Clock from the Simulation IO library. Connect one clock to each input pin.
Notice waveforms are being generated in the timing diagram window. To slow the waveform
movement, drag to the left the speed marker in the simulation palette in between two black
figures.
Time interval is assumed to be a unit time, which can be defined as any convenient value.
To change clock period, select a clock, open Simulation Parameters Dialog Box in Simulation
menu, change low and high intervals of the clock.
Clock period can be made visible. Select a clock with cursor, click right button to open Device
Parameter Box. Choose Device Info, choose Attributes, select delay.Dev, and choose Visible.
Once the clock period is visible, double click on it will open a dialog box where the period can be
changed.
Clicking on the sitting man in the simulation palette can stop simulation. Clicking once on the
walking man will move simulation one step further (Single Step Mode).
You may need to reset your simulation once in a while to make sure the signals are synchronized.
The U-turn button on the simulation palette will reset simulation to start at time 0.
2.10 Displaying and Changing gate delay time
Each gate has a default delay time of 1 time unit associated with it. The delay time could be set to
zero. To display device delay, select a device with cursor, click right button to open Device
Parameter Box. Choose Device Info, choose Attributes, select delay.Dev, and choose Visible.
Once device delay time is shown, click on it twice will open a delay time box. Device delay in the
box can be changed.
Another way to change device delay is to choose the device and select Simulation Parameters in
Simulation Menu. Type a new delay time in delay column and choose OK.
2.11 Setting trigger
Page 180 of the LogicWorks 4 reference manual explains the Trigger button that shows as a small
handgun in Simulation Palette.
Click on the button to open Trigger Setup Box. Choose EVERY, 10 TIME UNIT, and
REFERENCE LINE to add one reference bar on the timing diagram for every 10 time unit. Click
OK.
2.12 Verifying logic function of the circuit with clocks
In order to generate all possible input combinations of the three input signals, change the periods
of the clock signals so that they differ by multiple of 2s. For example, the three clocks can have
periods of 320, 160, and 80 respectively.
Click the U-turn button on Simulation Palette to reset simulation. Click the running man to run
simulator. Click the sitting man to stop it. Move the speed marker bar to change the speed of
simulation.
All input combinations should appear once during one period of the slowest clock, which is 320
units in this example.
You can check one such period to verify the function of the circuit.
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