Computer Science 324
Computer Architecture

Given equipment limitations (we have only three digital logic lab stations), we will need to have at least one group of two (though two groups of two is also fine).

When you enter the lab, you will be issued a collection of TTL chips. When you are not using the chips, please remember to return them to their antistatic containers. When the environment is dry, static electricity charges can damage the chips. The antistatic containers will help to dissipate any charges that otherwise might damage the chips.

You should have a number of different chips, including (but not limited to):

For this lab, you should complete solutions to each of the following questions. You will need to draw circuits, implement them, or both. Before moving from one question to the next, demonstrate your circuit to ensure credit for the implementation.

1. Other than those described above, what chips do you have? For each, indicate its purpose. (hint: see the attached chip overview)
2. As a warm-up exercise, construct a circuit that is equivalent to a 5-input AND gate. It lights LED 0 when SW0 through SW4 are all high (1). Strive to use as few chips as possible. Draw the pin-and-chip numbered logical circuit showing the chips you will use and how you will wire them before you begin wiring.
3. Implement a two-input exclusive-or gate. An exclusive-or gate generates a high signal when exactly one of its inputs is high. Your circuit should light LED 0 when exactly one of the two switches SW0 and SW1 are set high (1). You may use any combination of inverters, AND, OR, NAND, and NOR gates. Draw the pin-and-chip numbered logical circuit you will use before you begin wiring.
4. Extend the circuit in the previous step to light LED 1 when both switches are set high (1). This circuit is a half adder and sums two one-bit values.

   Move the wire from LED 0 to input "A" of the 7-segment display, and the wire from LED 1 to the "B" input. Finally, ground the "D1" input. What happens?

5. Draw a pin-and-chip numbered logical circuit diagram for how you could build the half adder of the previous step using only 74LS00 chips.
6. Show how you would wire together two half adders to make a full adder - a device that adds three bits together, generating a two-bit sum? (You need not actually wire it, just draw the pin-and-chip numbered logical circuit diagram here.)
7. (Extra credit) Connect SW0 through SW3 to inputs "A" through "D" respectively. Next, switch each of the blue dip switches in succession. What happens? Now, describe the purpose of the chip in the upper left corner of the board. How many gates do you think it requires?