【SV验证入门】接口在设计和验证中的使用

interface可以实现一定的逻辑。

interface信号端口变化，后期维护容易。

module的所有语法适合interface。

Modport设计用的多，验证常用clocking block。

// TODO-1 understand how the interface is defined and instantied
// TODO-2 check how to define methods inside interface and call them internally or externally
// TODO-3 understand how to prepare transactions, drive them and monitor them


module interface_type;
	typedef struct {
		bit [7:0] addr;
		bit [31:0] data;
		bit write;
		int id;
	} trans_t;
	
//struct print utility function
	function void trans_print(trans_t t, string name = "trans");
		string s;
		s = $sformatf("%s struct connect is as below \n", name);
		s = $sformatf("%s\taddr = 'h%2x \n", s, t.addr);
		s = $sformatf("%s\tdata = 'h%8x \n", s, t.data);
		s = $sformatf("%s\twrite = 'b%0b \n", s, t.write);
		s = $sformatf("%s\tid = 'h%8x \n", s, t.id);
		$display("%s", s);
	endfunction
	//使用示例
	initial begin
		trans_t my_trans;
  
		// 初始化结构体
		my_trans.addr = 8'hA5;
		my_trans.data = 32'h12345678;
		my_trans.write = 1'b1;
		my_trans.id = 32'hDEADBEEF;
  
		// 使用打印函数
		trans_print(my_trans, "my_trans");
  
		// 使用默认名称
		trans_print(my_trans);
	end
	//预期输出
	my_trans struct content is as below 
	addr  = 'ha5 
	data  = 'h12345678 
	write = 'b1 
	id    = 'hdeadbeef 

	trans struct content is as below 
	addr  = 'ha5 
	data  = 'h12345678 
	write = 'b1 
	id    = 'hdeadbeef 
	/*格式说明符：
	'h%2x: 十六进制显示，固定2位宽度
	'h%8x: 十六进制显示，固定8位宽度
	'b%0b: 二进制显示，自动宽度*/
	
	interface intf1;
		logic [7:0] addr;
		logic [31:0] data;
		logic write;
		int id;

    // transaction drive task
    task drive_trans(trans_t t);
      addr  <= t.addr ;
      data  <= t.data ;
      write <= t.write;
      id    <= t.id   ;
    endtask

    // transaction monitor task
    task mon_trans(output trans_t t);
      t.addr  = addr ;
      t.data  = data ;
      t.write = write;
      t.id    = id   ;
    endtask
  endinterface
  intf1 if1();

  initial begin
    trans_t trans_in[3], trans_mon[3];//数组
    // stimulus preparation
    trans_in = '{'{'h10, 'h1122_3344, 'b1, 'h1000}
                ,'{'h14, 'h5566_7788, 'b0, 'h1001}
                ,'{'h18, 'h99AA_BBCC, 'b1, 'h1002}
                };
    foreach(trans_in[i]) begin
      #10;
      // stimulus drive
      if1.drive_trans(trans_in[i]);
      trans_print(trans_in[i], $sformatf("trans_in[%0d]",i));
      #10;
      // stimulus monitor
      if1.mon_trans(trans_mon[i]);
      trans_print(trans_mon[i], $sformatf("trans_mon[%0d]",i));

      // transaction comparison
      if(trans_in[i] === trans_mon[i])
        $display("trans_in[%0d] === trans_mon[%0d]", i, i);
      else
        $error("trans_in[%0d] !== trans_mon[%0d]", i, i);
    end
  end
  /*预期输出
  trans_in[0] struct content is as below 
	addr  = 'h10 
	data  = 'h11223344 
	write = 'b1 
	id    = 'h00001000 

  trans_mon[0] struct content is as below 
	addr  = 'h10 
	data  = 'h11223344 
	write = 'b1 
	id    = 'h00001000 

  trans_in[0] === trans_mon[0]
  // ... 重复对于索引1和2*/
  添加断言检查:
  // 在接口中添加断言
  assert property (@(posedge clk) !$isunknown(addr)) else
	$error("Address has unknown bits");
  添加覆盖率收集:
  // 在接口中添加覆盖组
  covergroup trans_cg;
	coverpoint addr { bins low = {[0:127]}; bins high = {[128:255]}; }
	coverpoint write;
	cross addr, write;
  endgroup
  
endmodule