In: Electrical Engineering
Create a state meachine that encrypts an incoming digital bitstream using a D-flip-flop and a Mealy Meachine. The device have to meet these requirments:
A. The output of the encryption device matches the input bitstream until a certain set of bits is detected (such as 110). After this detection, the output is the complemented version of the input.
B. When a second bitstream 010 is detected, the output reverts to simply matching the input stream again. Please make both bitstreams that cause the switching action to be at least 3 bits in length.
Please include the following for the above questions:
1. A state graph for the machine.
2. The state tables, truth tables, and K-maps that you used to design the machine.
3. Give the example bitstream output demonstrating the machine in operation. Example bitstream: 0111010001110101
| 
 PRESENT STATE  | 
 INPUT  | 
 NEXT STATE  | 
 OUTPUT  | 
||||
| 
 Q2  | 
 Q1  | 
 Q0  | 
 X  | 
 Q2+  | 
 Q1+  | 
 Q0+  | 
 Z  | 
| 
 0  | 
 0  | 
 0  | 
 0  | 
 0  | 
 0  | 
 0  | 
 0  | 
| 
 0  | 
 0  | 
 0  | 
 1  | 
 0  | 
 0  | 
 1  | 
 0  | 
| 
 0  | 
 0  | 
 1  | 
 0  | 
 0  | 
 0  | 
 0  | 
 0  | 
| 
 0  | 
 0  | 
 1  | 
 1  | 
 0  | 
 1  | 
 0  | 
 0  | 
| 
 0  | 
 1  | 
 0  | 
 0  | 
 0  | 
 1  | 
 1  | 
 1  | 
| 
 0  | 
 1  | 
 0  | 
 1  | 
 0  | 
 1  | 
 0  | 
 0  | 
| 
 0  | 
 1  | 
 1  | 
 0  | 
 1  | 
 0  | 
 0  | 
 1  | 
| 
 0  | 
 1  | 
 1  | 
 1  | 
 0  | 
 1  | 
 1  | 
 0  | 
| 
 1  | 
 0  | 
 0  | 
 0  | 
 1  | 
 0  | 
 0  | 
 1  | 
| 
 1  | 
 0  | 
 0  | 
 1  | 
 1  | 
 0  | 
 1  | 
 0  | 
| 
 1  | 
 0  | 
 1  | 
 0  | 
 0  | 
 0  | 
 0  | 
 1  | 
| 
 1  | 
 0  | 
 1  | 
 1  | 
 0  | 
 1  | 
 1  | 
 0  | 
| 
 1  | 
 1  | 
 0  | 
 0  | 
 X  | 
 X  | 
 X  | 
 X  | 
| 
 1  | 
 1  | 
 0  | 
 1  | 
 X  | 
 X  | 
 X  | 
 X  | 
| 
 1  | 
 1  | 
 1  | 
 0  | 
 X  | 
 X  | 
 X  | 
 X  | 
| 
 1  | 
 1  | 
 1  | 
 1  | 
 X  | 
 X  | 
 X  | 
 X  | 
D Flip Flop output is delayed version of its input. Hence D Flop inputs can be same as Q2+, Q1+ and Q0+ outputs.
Karnaugh Mapping used to derive expressions for D2, D1 and D0 inputs of D Flip Flops.


Design is simulated in
logisim. Output observed for the input pattern "0111010001110101"
is "0000101110001000" as per design spec