Question

Design a door code detector (Mealy machine) that has two inputs S and Y where S is the start signal (by a push button) and Y gives the code that is a sequence of logic 0’s and 1’s (by a switch). The detector has one output Z (LED). To open the door (i.e., Z=1), you have to press the S button once and after that, input Y with sequence 100*10 where 0* means zero or more (i.e., any number of) logic 0.

For example, each of the following sequence will unlock the door: 1010, 10010, 100010, 1000010, …. 10000000000010, … Once a correct sequence to unlock the door has been detected, the machine goes back to the initial state unconditionally, and be ready for the next input sequence by pushing the S button and start another input sequence. The following gives a sample inputs and outputs.

Answer 1

state table

digital circuit

In the above circuit diagram I didn't draw some wire connections so that since it makes the circuit look messy but still I named the terminal of gates with terminals it has to be connected at input or respective flip flop output

Regarding kmaps I used a 5 variable kmap for simplification of next states ( Q2,Q1,Q0 ) and output Z