[HDLBits] Fsm3comb

The following is the state transition table for a Moore state machine with one input, one output, and four states. Use the following state encoding: A=2'b00, B=2'b01, C=2'b10, D=2'b11.

Implement only the state transition logic and output logic (the combinational logic portion) for this state machine. Given the current state (state), compute the next_state and output (out) based on the state transition table.

State	Next state		Output
	in=0	in=1
A	A	B	0
B	C	B	0
C	A	D	0
D	C	B	1

 

module top_module(
    input in,
    input [1:0] state,
    output [1:0] next_state,
    output out); //

    parameter A=0, B=1, C=2, D=3;
    reg [1:0] now;
    // State transition logic: next_state = f(state, in)
    always@(*) begin
        case(state)
            A:next_state<=in==0?A:B;
            B:next_state<=in==0?C:B;
            C:next_state<=in==0?A:D;
            D:next_state<=in==0?C:B;
        endcase
    end
    // Output logic:  out = f(state) for a Moore state machine
    assign out=(state==D)?1:0;
endmodule