Experiment 7: analysis of flip-flop circuits

ECE 1315 UMD 2008 Experiment 7

EXPERIMENT 7: ANALYSIS of FLIP-FLOP CIRCUITS

Use techniques developed in lecture to analyze the following flip-flop circuit. Note that the flip-flops are J-K(bar).

FIGURE 1: J-Kbar Flip-Flop Circuit

Create a State Transition Table and State Diagram for this circuit and include them in your report.

Now, implement the circuit as shown in the figure below. Note the following features of this circuit:



Figure 2: Circuit as Implemented

1. 
   Clock will be taken from Pin 22 of the LogiScan Socket. Set the frequency of this clock to 1000 milliseconds in the LogiScan software.
   
2. 
   The State Variable outputs will drive LEDs and it will be possible to determine the State of your machine by watching them flash on and off.
   
3. 
   The 74LS109 Dual J-K’ flip-flops have preset-bar and clear-bar inputs. Sending Vcc (+5 volts) to these inputs will disable them. Sending GND to the preset-bar inputs will make the flip-flops always put out a Logic 1, regardless of other input. Sending GND to the clear-bar inputs will make the flip-flops always put out a Logic 0. In your circuit, use a long wire to make it possible to START your circuit in the State 0 condition (F1, F0 = 00) by connecting the long wire to GND. Then, when the long wire is brought to Vcc, the circuit will start to function.
   

Have your Instructor verify the correct operation of your circuit: ___________________________

Now replace the AND gate in the circuit in Figure 1 with an OR gate and repeat the analysis. Make sure your report contains the new State Table and State Diagram. Replace the AND gate with an OR gate in Figure 2 and verify that the LEDs light as predicted by your State Diagram.

Have your Instructor verify the correct operation of your circuit: ___________________________

For the Conclusions of your report, answer the following questions:

1. 
   How many States are possible when using TWO 74LS106 chips?
   
2. 
   Comment on the possibility of building a One State synchronous machine and its potential usefulness.