Question

Given a binary string of zeros (0) and ones (1). You have to build a circuit that counts the number of occurrences of string '01' within the given string. For example, given string '01000110001001', there are 4 occurrences of '01' and output have to show number of occurance each time '01' occured. Use a FSM and a counter (built from D flip-flops) to implement this circuit. It is guaranteed that the number of occurrences is not more than 31 (you need a 5-bit counter). Insert the string using buttons'.Look at bold letter carefully then answer and provide Logisim circuit...

Answer 1

For the counter we will design a 5 bit asynchronous counter.

In asynchronous counter clock is iven only to first flipflop. The clock for subsequent flip-flops is connetced to Qbar of previous flip-flop.

Output y of FSM is given as enable to the counter by means of a 2:1 Multiplexer. If Y = 1, the counter counts up else it stays in previous count value.

Counter outputs are Qe,Qd,Qc,Qb and Qa where Qe is Most Significant Bit.

Final circuit is as follows