CE121L - Microprocessor System Design
Laboratory 1
Week of January 9, 1995

During this introductory lab, you will be checking out lab kits and documentation, purchasing parts kits, and using the oscilloscopes to measure an RC circuit.

PreLab

This section usually is a list of things to do before your lab session. This week, it includes things to do at the start of lab.

1. Begin the table of contents in your lab notebook, and date and number (if not already numbered) the page you will be recording today's work on. You should copy the circuit diagram below into your notebook before your lab session.
2. Purchase a parts kit and check out a wirewrap tool.

Laboratory Discussion

This week, we'll discuss the oscilliscopes and wire wrapping.

Laboratory

We are going to wirewrap a simple digital circuit and use the scope to examine its behaviour with and without large capacitive loads.

1. Wirewrap the '373 into your board (we'll remove it at the end of lab to practice unwrapping) such that it will act like a buffer.
2. Use the scope and a clock source to carefully measure the delay through the buffer, as well as its precise output voltages. If you can vary the amplitude of the clock source, also determine where the input threshold is. How does the chip's performance compare to the databook?
3. Using an intermediate single WW pin, wire the output of one buffer to the input of the next, and repeat your timing experiments. Are things as you expect?
4. WW a second single WW (near the first) to ground.
5. For each of the four capacitors, hook the capacitor up between the two WW pins (be sure to get the polarity correct with the electrolytic capacitors!) and repeat the experiment. Carefully draw the waveforms, including the clock input and the two buffer outputs.
6. Read the RC time constant from the scope. The RC node will rise from ground as soon the inverter input switches according to the equation . The time constant RC can be measured from the scope as how long it takes for to rise to 63% of its final value. Annotate this in your drawing of the scope screen, and also determine where the 50% point is.
7. Measure the capacitors (with the capacitance meter) you used. What resistance value appears to be in the circuit? Where is it?
8. Unwirewrap your board.