Connect/TwoKingdomsFactory

      Abstract/base Class

       Abstract / base类被定义为测试平台中agent的一部分。在此示例中，它是基类driver，包括用于连接到wishbone总线agent的其余部分的端口。

       Wrapper module

       创建包装器模块，其包括BFM和DUT的实例。concrete类在模块内定义，因此其域将是包装器模块。
       在包装器模块内部创建concrete类的实例。使用uvm_container将此实例的句柄放在配置数据库中。

       【此处需一幅图】

       以下是WISHBONE总线BFM的代码。

       module wishbone_bus_syscon_bfm #(int num_masters = 8, int num_slaves = 8,
                                                                       int data_width = 32, int addr_width = 32) ();
       ...
              // WISHBONE signals
              bit clk;
              bit rst;
               ...
              // WISHBONE bus arbitration logic
              ...
              //Slave address decode
              ...
              // BFM tasks
              //WRITE 1 or more write cycles
              task wb_write_cycle(wb_txn req_txn, bit [2:0] m_id = 1);
                   ...
              endtask

              //READ 1 or more cycles
              task wb_read_cycle(wb_txn req_txn, bit [2:0] m_id = 1, output wb_txn rsp_txn);
                   ...
              endtask

              // Monitor bus transactions
              task monitor(output wb_txn txn);
                   ...
              endtask

       endmodule

       下面是WISHBONE总线包装模块的代码。注意BFM（wishbone_bus_syscon_bfm）、slave memory（wb_slave_mem）和以太网MAC（eth_top）的实例。除了未示出或讨论的WISHBONE接口之外，MAC芯片还具有媒体独立接口（MII）。实际上，在此总线包装器中定义了两个concrete类 - driver和monitor，但仅显示和讨论了driver（wb_bus_bfm_driver_c）。

        module wb_bus_wrapper #(int WB_ID = 0);
        ...
               // WISHBONE BFM instance
               // Supports up to 8 masters and up to 8 slaves
               wishbone_bus_syscon_bfm wb_bfm();

               // WISHBONE 0, slave 0: 000000 - 0fffff
               wb_slave_mem #(mem_slave_size) wb_s_0 ( ... );

               // MAC 0
               // It is WISHBONE slave 1: address range 100000 - 100fff
               // It is WISHBONE Master 0
               eth_top mac_0 ( ... );

               // Concrete driver class
               class wb_bus_bfm_driver_c #(int ID = WB_ID) extends wb_bus_bfm_driver_base;
               ...
               endclass
               ...
        endmodule

        例如，如果concrete driver class接收到WISHBONE写入事务，则它调用其本地wb_write_cycle（） task，该 task又调用BFM内的wb_write_cycle（） task。

        module wb_bus_wrapper #(int WB_ID = 0);
        ...

               // Concrete driver class
               class wb_bus_bfm_driver_c #(int ID = WB_ID) extends wb_bus_bfm_driver_base;
                    ...

                    task run_phase(uvm_phase phase);
                         wb_txn req_txn;
                         forever begin 
                             seq_item_port.get(req_txn); // get transaction
                             @ ( posedge wb_bfm.clk) #1; // sync to clock edge + 1 time step
                             case(req_txn.txn_type) //what type of transaction?
                                   NONE: `uvm_info($sformatf("WB_M_DRVR_%0d",m_id),
                                                                            $sformatf("wb_txn %0d the wb_txn_type was type       NONE",req_txn.get_transaction_id()),UVM_LOW )
                                  WRITE: wb_write_cycle(req_txn);
                                  READ: wb_read_cycle(req_txn);
                                  RMW: wb_rmw_cycle(req_txn);
                                  WAIT_IRQ: fork wb_irq(req_txn); join_none
                                  default: `uvm_error($sformatf("WB_M_DRVR_%0d",m_id),
                                                                             $sformatf("wb_txn %0d the wb_txn_type was type illegal",req_txn.get_transaction_id()) )
                             endcase
                         end
                    endtask : run_phase 

                    // Methods
                    // calls corresponding BFM methods
                    //WRITE 1 or more write cycles
                    task wb_write_cycle(wb_txn req_txn);
                         wb_txn orig_req_txn;
                         $cast(orig_req_txn, req_txn.clone()); //save off copy of original req transaction
                         wb_bfm.wb_write_cycle(req_txn, m_id);
                         wb_drv_ap.write(orig_req_txn); //broadcast orignal transaction
                     endtask
                     ...
               endclass
               ...
        endmodule