fsm_3s

module fsm_3s(
  input a, b, clk, rst_b,
  output reg m, n, p
);

localparam s0 = 2'b00;
localparam s1 = 2'b01;
localparam s2 = 2'b10;
reg [1:0] st, st_next;

always @ (*) begin
  st_next = s0;
  case(st)
    s0: begin
      if (!a)
        st_next = s0;
      else
      if (a && !b)
        st_next = s1;
      else
        if (a && b)
          st_next = s2;
        end
    s1: st_next = s1;
    s2: begin
      if (!a)
        st_next = s2;
      else
      if (a)
        st_next = s0;
        end
  endcase
end

always @ (*) begin
  m = 1'd0;
  n = 1'd1;
  p = 1'd0;

  case(st)
    s0: begin
      if (!a)
        m = 1'd1;
      else
      if (a && b)
        p = 1'd1;
      else
      if (a && !b)
        n = 1'd0;
        end
    s1: begin
      p = 1'd1;
      m = 1'd1;
    end
    s2: begin
      if (!a)
        begin
          m = 1'd1;
          n = 1'd0;
        end
      else
        n = 1'd0;
      end
  endcase
end

always @ (posedge clk, negedge rst_b) begin
  if (!rst_b)
    st <= s0;
  else
    st <= st_next;
end

endmodule