Design a sequence detector, to detect four and multiple of four consecutive ones / zeros received on the serial input line X, using DFF.

Input=X

Output=Z

State Variables= QA & QB

0's detection, equations from KMAPS:

DA= Xbar. (QA XOR QB)

DB= Xbar. QBbar

Z=Xbar. QA. QB

1's detection, equations from KMAPS:

DA= X. (QA XOR QB)

DB= X. QBbar

Z=X. QA. QB