Due Monday January 26, 1998
We examine the detailed behavior of TTL logic gates and learn how to use light emitting diodes as a simple output means. Plan ahead on prelab work, inlab exercise, and data collection.
wire cutter,ICpuller,20gauge single solid conductor, component kit, breadboarding socket, CADET II, oscilloscope, LogicWorks, TTL data book.
Be careful inserting and removing IC's from the sockets. Removal is best done with an IC puller.
i. Read the description of individual features of CADET II.
ii. Exercise the CADET II checking out procedure.
iii. Use a map to show the internal connection of your breadboarding sockets.
i. Power: TTL requires a power supply of +5 Volts. Make sure power and ground are connected to the proper pins on the IC. Connecting power backwards will destroy the IC and may blow the fuse in the power supply. Always switch power off before making any change on the board to avoid inadvertent short circuits.
ii. Pin Assignment: Be familiar with TTL Data Book. Check the pin assignments drawn in the book.
iii. Decoupling Capacitors: It is standard practice to place a bypass capacitor across the supply to each one to five TTL IC's as close as possible to the chips. The bypass capacitors are used to reduce noise on the power and ground lines.
i. Mount 7404 on breadboard. Record Vout as Vin increments from 0 to 5 V with a step size of 0.25 V.
ii. Connect output to input. Measure the voltage level which is the so called switching threshold.
iii. Connect all inputs of 7404 to square wave. Check if there is any spike on the power pin. Check again after a 0.1 uF capacitor is mounted between power and ground pins.
Design a combinational logic that converts threebit binary code (w x y) to threebit gray code (a b c).
id wxy abc
0 000 000
1 001 001
2 010 011
3 011 010
4 100 110
5 101 111
6 110 101
7 111 100
i. Use LogicWorks to draw the schematic diagram and verify the results via simulation.
ii. Use LogicWorks to identify the input sequence which causes output glitches.
iii. Implement the circuit on breadboard. Use BCD 7 segment LED display to verify the output.
iv. Demonstrate the output glitches using oscilloscope and measure the width and magnitude of the glitch.
1. Use a chart to show Vout vs Vin of 7404 inverter in (5 i).
2. Note the switching threshold of 7404 in (5 ii).
3. Note the magnitude of the spike on the power pin before and after insertion of bypass capacitor in (5 iii).
4. Draw the logic diagram of the circuit in TTL components in (6 i).
5. Print the timing diagram using LogicWorks to show the output glitches in (6 ii).
6. Draw the wave form on oscilloscope to show the width and magnitude of the output glitch in (6 iv).