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 please(and provide Logisim circuit please)...

Answer 1

For counter we will use a 5 bit asynchronous counter.

In asynchronous counter Qbar of one flip flop is connected as clock of next flip flop.

The output Y of FSM is used as an enable for the counter. i.e. whenever Y becomes '1', the counter counts up else counter remains in previous state. This is done by use of the 2:1 Muliplexer.

Let the counter outputs be Qe,Qd,Qc,Qb,Qa where Qe is Most Significant Bit

Final Design combining FSM and counter