UVM验证平台加入field_automation机制

  (1)uvm_field宏实现field_automation机制

      UVM中需要逐字段地对transaction进行某些操作。这就是UVM中的 field_automation机制，使用uvm_field系列宏实现：

class my_transaction extends uvm_sequence_item;

   rand bit[47:0] dmac;
   rand bit[47:0] smac;
   rand bit[15:0] ether_type;
   rand byte      pload[];
   rand bit[31:0] crc;

   constraint pload_cons{
      pload.size >= 46;
      pload.size <= 1500;
   }

   function bit[31:0] calc_crc();
      return 32'h0;
   endfunction

   function void post_randomize();
      crc = calc_crc;
   endfunction

   `uvm_object_utils_begin(my_transaction)
      `uvm_field_int(dmac, UVM_ALL_ON)
      `uvm_field_int(smac, UVM_ALL_ON)
      `uvm_field_int(ether_type, UVM_ALL_ON)
      `uvm_field_array_int(pload, UVM_ALL_ON)
      `uvm_field_int(crc, UVM_ALL_ON)
   `uvm_object_utils_end

   function new(string name = "my_transaction");
      super.new();
   endfunction

endclass

        这里使用uvm_object_utils_begin和uvm_object_utils_end来实现my_transaction的factory注册，在这两个宏中间，使用uvm_field宏 注册所有字段。uvm_field系列宏随着transaction成员变量的不同而不同。
        当使用上述宏注册之后，可以直接调用copy、compare、print等函数，而无需自己定义。这极大地简化了验证平台的搭建，提 高了效率：

  (2)  引入field_automation机制的另外一大好处是简化了driver和monitor

my_model.sv

 
class my_model extends uvm_component;
   
   uvm_blocking_get_port #(my_transaction)  port;
   uvm_analysis_port #(my_transaction)  ap;

   extern function new(string name, uvm_component parent);
   extern function void build_phase(uvm_phase phase);
   extern virtual  task main_phase(uvm_phase phase);

   `uvm_component_utils(my_model)
endclass 

function my_model::new(string name, uvm_component parent);
   super.new(name, parent);
endfunction 

function void my_model::build_phase(uvm_phase phase);
   super.build_phase(phase);
   port = new("port", this);
   ap = new("ap", this);
endfunction

task my_model::main_phase(uvm_phase phase);
   my_transaction tr;
   my_transaction new_tr;
   super.main_phase(phase);
   while(1) begin
      port.get(tr);
      new_tr = new("new_tr");
      new_tr.copy(tr);
      `uvm_info("my_model", "get one transaction, copy and print it:", UVM_LOW)
      new_tr.print();
      ap.write(new_tr);
   end
endtask

my_scoreboard.sv 

class my_scoreboard extends uvm_scoreboard;
   my_transaction  expect_queue[$];
   uvm_blocking_get_port #(my_transaction)  exp_port;
   uvm_blocking_get_port #(my_transaction)  act_port;
   `uvm_component_utils(my_scoreboard)

   extern function new(string name, uvm_component parent = null);
   extern virtual function void build_phase(uvm_phase phase);
   extern virtual task main_phase(uvm_phase phase);
endclass 

function my_scoreboard::new(string name, uvm_component parent = null);
   super.new(name, parent);
endfunction 

function void my_scoreboard::build_phase(uvm_phase phase);
   super.build_phase(phase);
   exp_port = new("exp_port", this);
   act_port = new("act_port", this);
endfunction 

task my_scoreboard::main_phase(uvm_phase phase);
   my_transaction  get_expect,  get_actual, tmp_tran;
   bit result;
 
   super.main_phase(phase);
   fork 
      while (1) begin
         exp_port.get(get_expect);
         expect_queue.push_back(get_expect);
      end
      while (1) begin
         act_port.get(get_actual);
         if(expect_queue.size() > 0) begin
            tmp_tran = expect_queue.pop_front();
            result = get_actual.compare(tmp_tran);
            //直接调用compare函数，不需要自己定义compare函数

            if(result) begin 
               `uvm_info("my_scoreboard", "Compare SUCCESSFULLY", UVM_LOW);
            end
            else begin
               `uvm_error("my_scoreboard", "Compare FAILED");
               $display("the expect pkt is");
               tmp_tran.print();//直接调用print函数，不需要自己定义print函数
               $display("the actual pkt is");
               get_actual.print();//直接调用print函数，不需要自己定义print函数
            end
         end
         else begin
            `uvm_error("my_scoreboard", "Received from DUT, while Expect Queue is empty");
            $display("the unexpected pkt is");
            get_actual.print();
         end 
      end
   join
endtask

(3)使用field_automation机制后，可以 简化drv_one_pkt任务

class my_driver extends uvm_driver;

   virtual my_if vif;

   `uvm_component_utils(my_driver)
   function new(string name = "my_driver", uvm_component parent = null);
      super.new(name, parent);
   endfunction

   virtual function void build_phase(uvm_phase phase);
      super.build_phase(phase);
      if(!uvm_config_db#(virtual my_if)::get(this, "", "vif", vif))
         `uvm_fatal("my_driver", "virtual interface must be set for vif!!!")
   endfunction

   extern task main_phase(uvm_phase phase);
   extern task drive_one_pkt(my_transaction tr);
endclass

task my_driver::main_phase(uvm_phase phase);
   my_transaction tr;
   phase.raise_objection(this);
   vif.data <= 8'b0;
   vif.valid <= 1'b0;
   while(!vif.rst_n)
      @(posedge vif.clk);
   for(int i = 0; i < 2; i++) begin 
      tr = new("tr");
      assert(tr.randomize() with {pload.size == 200;});
      drive_one_pkt(tr);
   end
   repeat(5) @(posedge vif.clk);
   phase.drop_objection(this);
endtask

task my_driver::drive_one_pkt(my_transaction tr);
   byte unsigned     data_q[];
   int  data_size;
   
   data_size = tr.pack_bytes(data_q) / 8; 
        //调用pack_bytes将tr中所有的字段变成byte流放入data_q中
   `uvm_info("my_driver", "begin to drive one pkt", UVM_LOW);
   repeat(3) @(posedge vif.clk);
   for ( int i = 0; i < data_size; i++ ) begin
      @(posedge vif.clk);
      vif.valid <= 1'b1;
      vif.data <= data_q[i]; 
   end

   @(posedge vif.clk);
   vif.valid <= 1'b0;
   `uvm_info("my_driver", "end drive one pkt", UVM_LOW);
endtask

        第42行调用pack_bytes将tr中所有的字段变成byte流放入data_q中。 pack_bytes极大地减少了代码量。在把所有的字段变成byte流放入data_q中时，字段按照uvm_field系列宏书写的顺序排列。在上述 代码中是先放入dmac，再依次放入smac、ether_type、pload、crc。假如my_transaction定义时各个字段的顺序如下：

`uvm_object_utils_begin(my_transaction)
`uvm_field_int(smac, UVM_ALL_ON)
`uvm_field_int(dmac, UVM_ALL_ON)
`uvm_field_int(ether_type, UVM_ALL_ON)
`uvm_field_array_int(pload, UVM_ALL_ON)
`uvm_field_int(crc, UVM_ALL_ON)
`uvm_object_utils_end

        那么将会先放入smac，再依次放入dmac、ether_type、pload、crc。

my_monitor的collect_one_pkt可以简化成：

`ifndef MY_MONITOR__SV
`define MY_MONITOR__SV
class my_monitor extends uvm_monitor;

   virtual my_if vif;

   uvm_analysis_port #(my_transaction)  ap;
   
   `uvm_component_utils(my_monitor)
   function new(string name = "my_monitor", uvm_component parent = null);
      super.new(name, parent);
   endfunction

   virtual function void build_phase(uvm_phase phase);
      super.build_phase(phase);
      if(!uvm_config_db#(virtual my_if)::get(this, "", "vif", vif))
         `uvm_fatal("my_monitor", "virtual interface must be set for vif!!!")
      ap = new("ap", this);
   endfunction

   extern task main_phase(uvm_phase phase);
   extern task collect_one_pkt(my_transaction tr);
endclass

task my_monitor::main_phase(uvm_phase phase);
   my_transaction tr;
   while(1) begin
      tr = new("tr");
      collect_one_pkt(tr);
      ap.write(tr);
   end
endtask

task my_monitor::collect_one_pkt(my_transaction tr);
   byte unsigned data_q[$];
   byte unsigned data_array[];
   logic [7:0] data;
   logic valid = 0;
   int data_size;
   
   while(1) begin
      @(posedge vif.clk);
      if(vif.valid) break;
   end
   
   `uvm_info("my_monitor", "begin to collect one pkt", UVM_LOW);
   while(vif.valid) begin
      data_q.push_back(vif.data);
      @(posedge vif.clk);
   end
   data_size  = data_q.size();   
   data_array = new[data_size];
   for ( int i = 0; i < data_size; i++ ) begin
      data_array[i] = data_q[i]; 
   end
   tr.pload = new[data_size - 18]; //da sa, e_type, crc
   data_size = tr.unpack_bytes(data_array) / 8; 
   `uvm_info("my_monitor", "end collect one pkt", UVM_LOW);
endtask


`endif

        这里使用unpack_bytes函数将data_q中的byte流转换成tr中的各个字段。unpack_bytes函数的输入参数必须是一个动态数组，所 以需要先把收集到的、放在data_q中的数据复制到一个动态数组中。由于tr中的pload是一个动态数组，所以需要在调用 unpack_bytes之前指定其大小，这样unpack_bytes函数才能正常工作。