序列检测一定要用状态机？

那些年，你总是不停的说序列检测，每当有人谈到序列检测你便说自己会一、二、三段式moore、mealy型状态机，茴字有几种写法...

假设需要一个01101010比特流检测电路，并输出检测成果标志

当你开始考虑使用几个状态的时候，并好不容易写出以下代码的时候：

module detect2(
input clk,
input rst_n,
input din, 
output reg flag
);
 
//reg [2:0]state=3'b000;
parameter IDLE=3'b000,  //0
       state1=3'd1,  //1
       state2=3'd2,  //0
       state3=3'd3,  //1
       state4=3'd4,  //0
       state5=3'd5,  //1
       state6=3'd6,  //1
       state7=3'd7;  //0

reg [2:0]cur_state;
reg [2:0]nxt_state;
 
//第一个always块用于状态转移       
always@(posedge clk or negedge rst_n)
if(~rst_n)
 cur_state<=IDLE;
else 
 cur_state<=nxt_state;
 
/*
检测8'b01101010
*/       
always@(*) 
begin
 case(cur_state)
  IDLE:
   begin 
   if(din==1'b0)    
    nxt_state=state1; //0
   else 
    nxt_state=IDLE;
  end 
  state1: 
   begin
   if(1'b1==din)
     nxt_state=state2;  //10
   else 
     nxt_state=IDLE; 
   end 
  state2: 
   begin
    if(1'b0==din)
    nxt_state=state3;  //010
   else 
     nxt_state=IDLE; 
   end 
  state3: //有三个正确的接收数字
   begin
    if(1'b1==din)
    nxt_state<=state4;  //1010
   else 
     nxt_state=IDLE; 
   end 
  state4: 
   begin
    if(1'b0==din)
     nxt_state=state5;  //01010
   else 
     nxt_state=IDLE; 
   end 
  state5: 
   begin
    if(1'b1==din)
    nxt_state=state6;  //101010
   else 
     nxt_state=IDLE; 
   end 
  state6: 
   begin
    if(1'b1==din)
    nxt_state=state7;  //110_1010
   else             
     nxt_state<=state3;  //010
   end 
  state7: 
   begin
    nxt_state=IDLE;  
   end   
 default:;
 endcase 
end  

always@(posedge clk or negedge rst_n)
if(~rst_n)
 flag<=1'b0;
else if(cur_state==state7&&(1'b0==din))
 flag<=1'b1;
else 
 flag<=1'b0;

endmodule

答应我：下次试试移位寄存器可以吗？

module detect(
input clk,
input rst_n,
input din,
output flag
);
reg [7:0]bug;
always@(posedge clk or negedge rst_n)
if(~rst_n)
 bug<=8'hff;
else 
 bug<={din,bug[7:1]};

assign flag=bug==8'b0110_1010;
endmodule

一样的：