system verilog中%m和%0t啥意思

在SystemVerilog中，%m和%0t都是用于时间控制的系统任务。

%m表示当前仿真时间（从仿真开始到当前时刻的时间量），以毫秒为单位。例如，如果仿真时间为1.2秒，则%m的返回值为1200。

%0t表示上一个时间刻度的时间。时间刻度是指仿真时间中的最小单位。例如，如果时间刻度为1纳秒，那么%0t返回的是上一个纳秒的时间。

需要注意的是，%m和%0t都只能在initial块或task/function中使用，不能在always块中使用。

相关问题

I mean I'm quite new to system verilog, so I need you to show me the concrete code after modification, can you show me the code of the 10 ways of modification you just suggested? thanks a lot

Certainly! Here's the code for the 10 modifications I suggested:

1. Modify the values in both `t1` and `t2` class constructors to be random numbers instead of hard-coded values.

interface Int();
   class t1;
      integer a[string];
      function new;
         a["a"] =$random;
         a["b"] =$random;
         a["c"] =$random;
      endfunction
   endclass
   class t2;
      integer b[string];
      function new;
         b["aa"] =$random;
         b["bb"] =$random;
         b["cc"] =$random;
      endfunction
   endclass
   t1 inst1 =new;
   t2 inst2 =new;
endinterface

2. Add an additional class that extends `t1` and `t2` and overrides specific values with its own.

interface Int();
   class t1;
      integer a[string];
      function new;
         a["a"] =40;
         a["b"] =60;
         a["c"] =80;
      endfunction
   endclass
   class t2;
      integer b[string];
      function new;
         b["aa"] =44;
         b["bb"] =66;
         b["cc"] =88;
      endfunction
   endclass
   class t3 extends t1,t2;
      function new;
         super.new();
         a["a"] =100;
         b["bb"] =200;
      endfunction
   endclass
   t1 inst1 =new;
   t2 inst2 =new;
   t3 inst3 =new;
endinterface

3. Use a different data type for the `integer array[string]` variable, such as `real array[string]`.

interface Int();
   class t1;
      real a[string];
      function new;
         a["a"] =40;
         a["b"] =60;
         a["c"] =80;
      endfunction
   endclass
   class t2;
      real b[string];
      function new;
         b["aa"] =44;
         b["bb"] =66;
         b["cc"] =88;
      endfunction
   endclass
   t1 inst1 =new;
   t2 inst2 =new;
endinterface

4. Change the `virtual` keyword to `pure virtual` in the `Int` interface declaration.

interface Int();
   pure virtual class t1;
      integer a[string];
      function new;
         a["a"] =40;
         a["b"] =60;
         a["c"] =80;
      endfunction
   endclass
   pure virtual class t2;
      integer b[string];
      function new;
         b["aa"] =44;
         b["bb"] =66;
         b["cc"] =88;
      endfunction
   endclass
   t1 inst1 =new;
   t2 inst2 =new;
endinterface

5. Replace the `initial` block with a `task` or `function` that takes in the `Int` interface as an argument and returns the `array` variable.

interface Int();
   class t1;
      integer a[string];
      function new;
         a["a"] =40;
         a["b"] =60;
         a["c"] =80;
      endfunction
   endclass
   class t2;
      integer b[string];
      function new;
         b["aa"] =44;
         b["bb"] =66;
         b["cc"] =88;
      endfunction
   endclass
   task test;
      input Int in;
      integer array[string];
      begin
         #1;
         array =in.inst1.a;
         $display("testint.inst1.a =%p", in.inst1.a);
         $display("array = %p", array);
         #2;
         array =in.inst2.b;
         $display("testint.inst2.b =%p", in.inst2.b);
         $display("array =%p", array);
      end
   endtask
   t1 inst1 =new;
   t2 inst2 =new;
endinterface
module top;
   Int in();
   initial begin
      test(in);
   end
endmodule

6. Add a `bit [31:0]` variable to both `t1` and `t2` classes and modify the constructor functions to set it to the sum of the other values.

interface Int();
   class t1;
      integer a[string];
      bit [31:0] sum;
      function new;
         a["a"] =40;
         a["b"] =60;
         a["c"] =80;
         sum =a["a"] +a["b"] +a["c"];
      endfunction
   endclass
   class t2;
      integer b[string];
      bit [31:0] sum;
      function new;
         b["aa"] =44;
         b["bb"] =66;
         b["cc"] =88;
         sum =b["aa"] +b["bb"] +b["cc"];
      endfunction
   endclass
   t1 inst1 =new;
   t2 inst2 =new;
endinterface

7. Create a new interface that extends `Int` and adds additional methods or variables.

interface Int();
   class t1;
      integer a[string];
      function new;
         a["a"] =40;
         a["b"] =60;
         a["c"] =80;
      endfunction
   endclass
   class t2;
      integer b[string];
      function new;
         b["aa"] =44;
         b["bb"] =66;
         b["cc"] =88;
      endfunction
   endclass
   t1 inst1 =new;
   t2 inst2 =new;
endinterface

interface Int2 extends Int();
   parameter int MAX_ARRAY_SIZE =100;
   function void print_array();
      for (int i =0; i < MAX_ARRAY_SIZE; i++) begin
         $display("a[%0d] = %0d", i, inst1.a[i]);
      end
   endfunction
endinterface

module top;
   Int2 in();
   initial begin
      in.print_array();
   end
endmodule

8. Modify the `testint` variable to be a `typedef` of the `Int` interface instead of a `virtual` instance.

typedef Int testint_t;
testint_t in =new();

9. Change the `integer` data type to `bit [7:0]` for all instances of `integer` in the code.

interface Int();
   class t1;
      bit [7:0] a[string];
      function new;
         a["a"] =40;
         a["b"] =60;
         a["c"] =80;
      endfunction
   endclass
   class t2;
      bit [7:0] b[string];
      function new;
         b["aa"] =44;
         b["bb"] =66;
         b["cc"] =88;
      endfunction
   endclass
   t1 inst1 =new;
   t2 inst2 =new;
endinterface

10. Add assertions to the code to ensure that the values in `testint.inst1.a` and `testint.inst2.b` are always greater than zero.

interface Int();
   class t1;
      integer a[string];
      function new;
         a["a"] =40;
         a["b"] =60;
         a["c"] =80;
         assert(a["a"] > 0) else $error("Value of a[a] is not greater than zero");
         assert(a["b"] > 0) else $error("Value of a[b] is not greater than zero");
         assert(a["c"] > 0) else $error("Value of a[c] is not greater than zero");
      endfunction
   endclass
   class t2;
      integer b[string];
      function new;
         b["aa"] =44;
         b["bb"] =66;
         b["cc"] =88;
         assert(b["aa"] > 0) else $error("Value of b[aa] is not greater than zero");
         assert(b["bb"] > 0) else $error("Value of b[bb] is not greater than zero");
         assert(b["cc"] > 0) else $error("Value of b[cc] is not greater than zero");
      endfunction
   endclass
   t1 inst1 =new;
   t2 inst2 =new;
endinterface