The Basics of Digital Logic

Lesson 6

Ok, now it's time to try some of this on your own.  We have added an extra menu and some tool-bars to help you do your own drawing.  You are going to create a circuit containing a 3-input AND gate and simulate it.  So that you will have a permanent record of your first digital circuit, you may print the drawing, or save it to a file, or both.  Don't try to use the Internet Explorer menus or tool-bars to interact with your drawing.

• The first step is to locate the gate-selector on the drawing tool bar.  It looks like this: .
• Click on the little arrow at the right, and a list of gate names will drop down.
• Click on the gate name AND3.  This will be the fourth item in the list.
• Now go down to the white drawing area right below this text and click somewhere in the middle of this area. A new AND gate will appear in this area.
• Click the following button when you are finished.    Good! The remaining instructions are below the drawing area. Go there now.

• Go back to the gate-selector and choose Primary Input.   This will be the first item in the list.  You will need to use the scroll-bar to the right of the list to see this item, because AND3 will be shown at the top of the list.
• Go to the drawing area and draw three primary input symbols in a column on the left side of the drawing area.  One click draws one input symbol.
• Click Here when you are finished.
• Go to the gate-selector and choose Primary Output.  This is the second item in the list.
• Go to the drawing area and draw one primary output symbol on the right side of the drawing area.
• Click Here when you are finished.
• On the tool bar, near the gate-selector, is the wire shape tool bar.  Find the horizontal dog-leg button.  It looks like this:
• Click the horizontal dog-leg button.
• Now draw wires between the primary input symbols and the input ports of the gate.   You draw a wire by clicking (and holding) on the port of the primary input symbol, holding the button down, and dragging the mouse to the input port of the gate.  The line will appear to be diagonal, but once you release the mouse, a 3-segment line, called a dogleg, will appear. Make sure the ports turn red.
• Draw a wire between the output of the gate and the primary output symbol.
• Click Here when you are finished.

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