資工趴趴熊的小天地

狀態圖

 

密利模型

輸出值是目前狀態和輸入兩者的函數。

在時脈週期內，若輸入改變則輸出可能改變。

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密利模型--design   bench

module Mealy_Zero_Detector (
  output reg y_out, 
  input x_in, clock, reset
);
  reg [1: 0]	state, next_state;
  parameter	S0 = 2'b00, S1 = 2'b01, S2 = 2'b10, S3 = 2'b11;
  //將每一個部分輸入好

  always @ (posedge clock, negedge reset)	// D型正反器觸發

    if (reset == 0) state <= S0;  若rst=0時，將S0輸入給state
    else state <= next_state;  //若rst=1時，將nest sate 輸入給state

  always @ (state, x_in) // Form the next state  // 有幾種狀況
    case (state)
      S0:	if (x_in)   next_state = S1; else next_state = S0;
      S1: if (x_in) 	  next_state = S3; else next_state = S0;
      S2:	if (~x_in) next_state = S0; else next_state = S2;
      S3: if (x_in)   next_state = S2; else next_state = S0;
    endcase 

  always @ (state, x_in) //y_out輸出的方式
    case (state)
      S0:	y_out = 0;
      S1, S2, S3: y_out = ~x_in;
    endcase 
endmodule 

密利模型--test   bench

module t_Mealy_Zero_Detector;
  wire  t_y_out; 
  reg	t_x_in, t_clock, t_reset;

Mealy_Zero_Detector M0 (t_y_out, t_x_in, t_clock, t_reset);

initial #200 $finish;
initial begin t_clock = 0; forever #5 t_clock = ~t_clock; end

initial fork
       t_reset = 0;
  #2 t_reset = 1;
  #87 t_reset = 0;
  #89 t_reset = 1;
  #10 t_x_in = 1;
  #30 t_x_in = 0;
  #40 t_x_in = 1;
  #50 t_x_in = 0;
  #52 t_x_in = 1;
  #54 t_x_in = 0;
  #70 t_x_in = 1;
  #80 t_x_in = 1;
  #70 t_x_in = 0;
  #90 t_x_in = 1;
  #100 t_x_in = 0;
  #120 t_x_in = 1;
  #160 t_x_in = 0;
  #170 t_x_in = 1;
  
  join
endmodule

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