ELE201 Digital Circuit Design Test 3 Nov 22 2011 NAME Instructions This is a closed book closed notes exam You have 60 minutes to complete the problems Note that the problems have different weights plan your efforts accordingly There are multiple versions of this test hence your answers might not match those of your friends Prob Max score 1 30 2 30 3 20 4 20 Total 100 Your score 1 State machine design 30 points A state diagram with input X is shown below using state variables Q1Q0 Design a circuit to implement this diagram using two JK flip flops The unused state should be considered as a don t care to keep the logic as simple as possible Determine what happens to the unused state add its transition to the state diagram 11 X 10 X J1 K1 J0 K0 01 2 Counter design 30 points You are to design a portion of a 4 bit counter with count sequence 0 3 6 9 12 C 0 3 Assuming that the flip flop variables are Q3Q2Q1Q0 design the next state logic for Q1 I want answers for both D and JK flip flop implementations To keep the result as simple as possible assume that all unnamed states are don t cares J1 K1 D1 3 State Diagram 20 points Recently I purchased a new high tech clothes dryer with a dry clothes sensor Once I power it up its action is as follows the dryer sits idle waiting for me to press a start button once started the dryer s controller applies heat and rotates the drum holding the clothes in a clockwise direction while the sensor indicates that the clothes are still damp the heat stays on and the drum continues to rotate once the sensor determines that the clothes are dry both the heat and drum rotation are stopped and the dryer pauses for 30 seconds after pausing the drum rotates in the opposite direction counter clockwise with the heat off for 60 seconds to fluff the clothes the drum again stops a buzzer goes off for 10 seconds and the dryer returns to the idle state You are to develop a finite state machine for this controller First clearly list all of the inputs and outputs necessary and give them suitable names if you need any additional subsystems fully specify them Second draw your state diagram on the next page fully labeling it with the relevant input and output values INPUTS OUTPUTS STATE DIAGRAM 4 Debugging a Circuit 20 points The state diagram for a 3 bit 5 counter with binary count sequence 0 1 2 3 4 0 1 etc with flip flop outputs Q2Q1Q0 is shown Imagine that one of your classmates built the circuit shown Unfortunately it does not quite implement the desired state diagram Specifically one of the connections in incorrect the result is that the count sequence is 0 1 2 3 0 1 2 etc repeating too early Find and correct the error in the circuit Describe your correction in the box provided 000 001 100 011 J Q2 J C K clock Correction 010 J Q1 C Q2 K Q0 C Q1 1 K Q0