For each decimal number given by the binary representation n $3$ n $2$ n $1$ and n $0(4$ bits$),$ your circuit should display the correct segments on the figure to the right. For

instance, if your number is $0101,$ or $5$ in decimal, the segments a$,$ c$,$ d$,$ f$,$ and g should be lit up and the others should not be$.$

Create a truth table using Microsoft Excel $($not on paper; this has a purpose!$)$ for the seven$-$segment decoder. The truth table should have inputs labeled: n$3,$ n$2,$ n$1,$ n$0$

where n $3$ is the most significant input. The outputs of the table should be labeled as $a,b,c,d,e,f,$ and $g$ corresponding to the segments in the figure shown to the right.

The file should contain enough rows to account for input values from $0$ to $15(0$ to F in hexadecimal$),$ activating the appropriate segments to display these values. For

any value above $9,$ an $\text{'}E\text{'}($for Error$)$ should be displayed by activating the appropriate segments. Save the file as sevenTable.xlsx

Open Logisim$-$evolution and use SAVE AS to save the empty project as seven$\_$seg.circ

The top folder in the Libraries tree should now be seven$\_$seg. Right click and add a new circuit called Display. You may delete the circuit labeled main.

Right$-$click on that top folder and select Add Circuit and add another circuit called SevenSegDecoder. You can also get this option from the Project menu.

Good news! You don't have to create those nasty logical expressions for each of the LEDs! You get to use the tool in Logisim$-$evolution that you wish you could have

used for the previous lab.$$

Open the Combinational Analysis Tool from the Window menu. We will use this to create a third circuit, called SevenSegPLD. We will use the Combinational

Analysis tool which will allow Logisim$-$evolution to generate the circuit based on your truth table. Click the Input tab and add the appropriate input names $($n$3,$ n$2,$ n$1,$

and n $0$ where n $3$ is the most significant bit$)$ and click Add. Similarly, click the Output tab and add the output names $($a$,$ b$,$ c$,$ d$,$ e$,$ f$,$ and g$)$ corresponding to the

segments listed in the above figure. Click on Table and load the correct output values into the truth table by copying and pasting from your spreadsheet. $($Note: you

can copy all of your output values from your spreadsheet and paste them into the truth table all at one time.$)$

Click Build Circuit. Be sure to name the circuit SevenSegPLD and make sure the destination is set to seven$\_$seg.circ

Close the Combinational Analysis window.

Now you should have three circuits, $($Display$,$ SevenSegDecoder, and SevenSegPLD$)$ in your project library.

NOTE: Double$-$clicking on a circuit displays its contents. Single$-$clicking on a circuit allow you to create an instance of it as a part in another circuit.

NOTE: Logisim$-$evolution draws a magnifying glass over the icon of the circuit currently being viewed; the current circuit name also appears in the window's title bar.

REMEMBER: the n $3$ input of your SevenSegPLD circuit is the most significant. This means that it will appear as the top input when added as a subcircuit. Keep this

in mind when wiring.

Double$-$click on the SevenSegDecoder circuit. You should see an empty breadboard at this point.

Create an instance of the SevenSegPLD circuit as a part $($Click on the circuit one time!$)$ and place it $($by clicking again$)$ on the SevenSegDecoder's breadboard. Move

the part to the middle of the breadboard.

Add the following I$/$O:

$14-$bit input $-$ labeled BCD$\_$In

$11-$bit input $-$ labeled DP$\_$In

$19\mathrm{.}81-$bit outputs $-$ each labeled corresponding to the segment they will be attached to$.$ Also one labeled DP$\_$Out.

Connect DP$\_$In to DP$\_$Out. This is simply a pass through.

Connect the rest of the inputs and outputs to the SevenSegPLD circuit so as to allow a $4-$bit BCD number to be the input, and the correct outputs to be activated.

Test all possible inputs and the outputs they generate.

Now, double$-$click the Display circuit and bring the SevenSegDecoder into the Display circuit as a part. You have now built a circuit within a circuit within a circuit!

Place the part into the middle portion of the breadboard.

Add a $7-$Segment Display device $($found in the Input$/$Output library folder on the left$)$ to the right of the SevenSegDecoder.

Connect the output of the SevenSegDecoder to the inputs of the $7-$Segment Display. Note the previous images to make proper connections.

Add the following I$/$O:

$14-$bit input labeled BCD

$11-$bit input labeled DP

Connect the I$/$O that was just added to the circuit.

Test all possible input values again to make sure that the correct value is displayed on the display device.