学步园

Continuous assignment statements drive nets (wire data type). They represent structural connections.

连续赋值语句能够驱动线网类型（net类型 如wire). 它们用来表示结构化的连接。

• They are used for modeling Tri-State buffers. // 它们用来为三态缓冲器建模
• They can be used for modeling combinational logic. //它们可以用来为组合逻辑建模
• They are outside the procedural blocks (always and initial blocks).//它们在过程块（always block， initial block之外，
• The continuous assign overrides any procedural assignments. //连续赋值语句，可以覆盖任何过程性的赋值
• The left-hand side of a continuous assignment must be net data type. //连续性赋值语句的左操作数必须是一个线网类型，net类型。

syntax : assign (strength, strength) #(delay) net = expression; // 连续赋值语句的语法。

  1 module adder_using_assign ();
  2 reg a, b;
  3 wire sum, carry;
  4 
  5 assign  #5  {carry,sum} = a+b; 
  6 
  7 initial begin
  8   $monitor (" A = %b  B = %b CARRY = %b SUM = %b",a,b,carry,sum);
  9    #10  a = 0;
 10   b = 0;
 11    #10   a = 1;
 12    #10   b = 1;
 13    #10   a = 0;
 14    #10   b = 0;
 15    #10  $finish;
 16 end
 17 
 18 endmodule 

You could download file adder_using_assign.v here

  1 module tri_buf_using_assign();
  2 reg data_in, enable;
  3 wire pad;
  4 
  5 assign pad = (enable) ? data_in : 1'bz;
  6 
  7 initial begin
  8   $monitor ("TIME = %g ENABLE = %b DATA : %b PAD %b", 
  9     $time, enable, data_in, pad);
 10    #1  enable = 0;
 11    #1  data_in = 1;
 12    #1  enable = 1;
 13    #1  data_in = 0;
 14    #1  enable = 0;
 15    #1  $finish;
 16 end
 17 
 18 endmodule

You could download file tri_buf_using_assign.v here

Continuous Assignments may have a delay specified; only one delay for all transitions may be specified. A minimum:typical:maximum delay range may be specified.

连续赋值语句可能有一个时延指派值；有可能为所有的传输指派一个唯一的时延值。一种（最小值：典型值：最大值）的时延区间肯能被指派。

  1 module tri_buf_using_assign_delays();
  2 reg data_in, enable;
  3 wire pad;
  4 
  5 assign #(1:2:3) pad = (enable) ? data_in : 1'bz;
  6 
  7 initial begin
  8   $monitor ("ENABLE = %b DATA : %b PAD %b",enable, data_in,pad);
  9    #10  enable = 0;
 10    #10  data_in = 1;
 11    #10  enable = 1;
 12    #10  data_in = 0;
 13    #10  enable = 0;
 14    #10  $finish;
 15 end
 16 
 17 endmodule

You could download file tri_buf_using_assign_delays.v here