When s 1 x1 outputs the value of y and x0 outputs LOW TODO pre lab Fill in a

# When s 1 x1 outputs the value of y and x0 outputs low

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When s = 1, x1 outputs the value of y , and x0 outputs LOW. TODO (pre-lab): Fill in a truth table for the demultiplexer. s y x0 x1 0 0 0 1 1 0 1 1 1
TODO (pre-lab): Provide a circuit diagram for a 1-to-2 demultiplexer . Your diagram should use specific gates, it should NOT be the symbol shown below. The symbol for a 1-to-2 demultiplexer looks like the opposite of a multiplexer: In the previous lab, you saw that you could make a 1-of-4 multiplexer out of three 1-of-2 multiplexers. TODO (pre-lab): Provide a diagram of how you could make a 1-to-4 demultiplexer using 1-to-2 demulti- plexers (the symbol shown above). Your 1-to-4 demultiplexer will have 4 outputs: x0 , x1 , x2 , and x3 . The table below shows which output returns the value of y for different values of select1 and select0 . Your diagram must agree with the table. select1 select0 output that returns y 0 0 x0 0 1 x1 1 0 x2 1 1 x3 2 Demultiplexers TODO: Using the circuit diagram from the third TODO of your prelab, implement a 1-to-2 demultiplexer on the Magic Box. Leave enough room on your breadboard to wire up a multiplexer for the next part of this lab. Verify that it works as anticipated and then show it to your TA. 2
Next, you will be implementing a multiplexer-demultiplexer scheme on the Magic Box. The instructions below detail this process: 1. Turn off the power to the Magic Box while wiring. 2. Wire up a 1-of-2 multiplexer chip (LS157 ) next to your demultiplexer. Connect power , ground , and the enable input. (Remember from Lab 3 that enable should be low .) Also connect one pair of inputs, a and b , to two switches. 3. Connect the two select inputs by wiring the s input of the demultiplexer chip to the s input of the multiplexer. Now, the multiplexer and demultiplexer share the same select signal. 4. Next, connect the out output of the multiplexer to the y input of the demultiplexer. The multiplexer and demultiplexer should now be connected as shown in this diagram: 5. Verify that your mux-demux scheme works as expected by trying out different combinations of