Lab 4: Digital Logic
This week, we will be designing simple circuits that solve interesting problems; some of these will be useful
in the next unit, when we learn how computer processors and memory work. We'll use the SimCir circuit simulation
tool.
By the end of this lab, you should be comfortable with:
- Using SimCir
- Constructing circuits using the Sum-of-Products or other techniques.
Lab Tasks:
- Visit The SimCir page, and download simcir121.zip.
- Open the file simcir.html, and construct a circuit with a battery connected to a toggle switch, which is
connected to an LED. Flip the switch, and check that the LED changes.
- Your workspace (to construct circuits in) is not very large. Increase it by opening the file simcir.html in
a text editor, and changing the values for width and height.
- Construct a circuit with three inputs A,B, and C, which has the output A . (B + C).
- Construct a circuit that has this truth table.
| A | B | C | Output |
| 0 | 0 | 0 | 0 |
| 0 | 0 | 1 | 1 |
| 0 | 1 | 0 | 0 |
| 0 | 1 | 1 | 0 |
| 1 | 0 | 0 | 1 |
| 1 | 0 | 1 | 0 |
| 1 | 1 | 0 | 1 |
| 1 | 1 | 1 | 0 |
- Write out a truth table for this circuit. Can you find a simpler circuit
with the same truth table?
(Note that to see the circuit, you will have to save the cml file to your simcir directory, and edit the
simcir.html file.)
- Construct a sequential memory circuit, following the outline in your handout.
- Design a circuit for a 2-bit decoder.
- Design a circuit for a 3-bit encoder.
- Design a circuit with 3 inputs, which outputs 1 if the majority of its inputs are 1, and 0 if the majority
of the inputs are 0.