CS467 -- Advanced Logic Design
Lab 2 -- Building Circuits on a Breadboard
Handed out Monday October 5th
Due Monday October 12th

Overview

This lab will involve building a simple circuit on the breadboard in the design kit. You can work on this lab in teams of two if you like. Although I'm giving you until next Monday to demonstrate this circuit, you should be able to complete the circuit and demo it in your T-H lab section. The main point of this lab is to get some experience with circuit implementations, switches, LEDs, looking up documentation on data sheets, using lab equipment, and wiring things up on the breadboards. Remember that even though you may be working in a team you are required to know how to do everything even if you don't do everything.

For this lab you'll need:

• Your DesignKit, specifically:
  • A bar-graph LED display
  • A DIP-switch
  • Resistor packs
  • a few ICs
• Two momentary pushbutton switches (available in the CSE467 box)
• A multi-meter (available in the second drawer of the red cabinet, return after use).

Using the Breadboard

Please read the document on the web about using the DesignKit for prototyping!

What Circuit to Build

For this lab you will build a debounced switch using one of the push-button switches and a non-debounced switch using the other. You will need to use the multi-meter to determine how the pushbutton switch outputs behave (i.e. which one is connected when the button is not pressed, which one when it is pressed, and which one is the common pin).

You will also use a counter chip from your DesignKit and connect the four outputs of the counter to LEDs from the LED pack. You will alternatively connect the non-debounced and debounced switch to the clock input of the counter chip to see the effects of switch bouncing. You will also use your signal generator from the DesignKit to drive the counter to watch the effect of different clock rates.

See the DesignKit documentation for information on using the LED packs and driving the LEDs. You will need to use a DIP switch to control the reset input of the counter, and pay attention to all the inputs of the counter. You will need to tie some of them high or low to get the counter to operate correctly. Use the NOR-based debouncing circuit from page 317 of your textbook to debounce the switch. You will need to find the data sheets for the counter chip that you're using and other gates (NOR, inverter, etc) either in the databooks in the lab or from the web (i.e. find a chip manufacturer and see if their web page has databooks online). Remember to connect power and ground to the chips!

What to Do

• Design a circuit for counter, LEDs, and debouncer. Draw this schematic neatly by hand, or use Foundation to draw the schematic. If you use Foundation you will need to create symbols for devices that are not available in the Xilinx library (like the counter chip, the LEDs, the resistors, etc).
• Build a circuit that uses a counter chip to drive four LEDs.
• Wire up two pushbutton switches: one debounced, the other not debounced.
• Use those two switches to demonstrate to the TA the effects of switch bouncing.
• Use your signal generator to drive the clock input of the counter to demonstrate the effects of clock rate on the LED signals.
• Use a multi-meter to measure the voltage drop and current across the LED. To measure current you'll need to reposition the leads of the multi-meter and put the multi-meter in series with the LED. Report the current and voltage drop.
• Turn in your schematic (signed by the TA after you demonstrate the circuit), and include what you measured for voltage drop and current across an LED.
• How would you design a switch debouncer if all you had was a 74LS00 chip with your switch (i.e. NAND instead of NOR)? Draw this schematic and turn it in with the other.
• Write down a very brief description of what each team member did and have both team members sign it and turn it in with the test of the documentation.