双段式状态机的写法，实现010序列检测

parameter idle = 2'd0; 
parameter st1 = 2'd1;
parameter st2 = 2'd2;
  
reg [1:0] cur_state; 
always@(posedge  clk_i or negedge rst_n )   begin
  if(!rst_n) 
		cur_state <= idle;
  else 
		cur_state <= next_state;
end
  
reg [1:0] next_state; 
always@ (*)  begin
	 case (cur_state)
		idle :
			if(vs_i == 0)
				next_state = st1;
			else
				next_state = idle;
		st1 :
			if(vs_i == 1)
				next_state = st2;
			else
				next_state = st1;
		st2:
			if(vs_i == 0)
				next_state = idle;
			else
				next_state = idle;
		default:
			next_state = idle;
	 endcase
  
end

reg flag;
always@(posedge  clk_i or negedge rst_n )   begin
  if(!rst_n) 
		 flag <= 0;
  else if(cur_state == st2 && vs_i == 0)
		 flag <= 1;
	else
		flag <= 0;
end

其他序列检测可参照例程实现