virtual class uvm_subscriber #(type T=int) extends uvm_component;

  typedef uvm_subscriber #(T) this_type;

  uvm_analysis_imp #(T, this_type) analysis_export;

  function new (string name, uvm_component parent);

    super.new (name, parent);

    analysis_export = new ("analysis_imp", this);

  endfunction

  pure virtual function void write (T, t);

endclass

class my_coverage extends uvm_subscriber #(bus_pkt);

  covergroup cg_bus;

    ...

  endgroup

  virtual function void write (bus_pkt pkt);

    cg_bus.sample ();

  endfunction

endclass

class my_env extends uvm_env;

  ...

  virtual function void connect_phase (uvm_phase phase);

    super.connect_phase (phase);

    my_agent.custom_ap.connect (my_cov.analysis_export);

  endfunction

endclass

class uvm_ip_subscriber extends uvm_subscriber;

  //這裡使用FIFO通信而不是IMP，大大降低了工作量

  uvm_tlm_analysis_fiof#(dma_trans)            dma_monitor_to_sub_fifo[1];

  extern function new(string name, uvm_component parent);

  extern virtual function write(T t);

  extern virtual task get_dma_trans();

  extern virtual task run_phase(uvm_phase phase);

  //coverage group

  covergroup ostd_cfg_group;

    option.per_instance = 1;

    ostd: coverpoint(reg_cfg_trans.reg_wr_ostd[7:0]){

            bins udb_0    =    {0};

            bins udb_1    =    {[1:8]};

            bins udb_2    =    {[9:16]};

            bins udb_3    =    {[17:254]};

            bins udb_4    =    {255};

    }

  endgroup

endclass: uvm_ip_subscriber

function uvm_ip_subscriber::new(string name, uvm_component parent);

  super.new();

  dma_monitor_to_sub_fifo[0] = new("dma_monitor_to_sub_fifo_0", this);

  //創建covergroup

  ostd_cfg_group = new();

endfunction: new

//必須得重寫write這個純虛函數

function uvm_ip_subscriber::write(T t);

endfunction: write

task uvm_ip_subscriber::get_dma_trans();

  dma_monitor_to_sub_fifo[0].get(tr);

  $cast(tr_clone, tr);

  reg_cfg_tr_q[0].push_back(tr_clone);

  if(reg_cfg_tr_q[0].size() > 0) begin

    reg_cfg_trans = reg_cfg_tr_q[0].pop_front();

    //採樣

    ostd_cfg_group.sample();

  end

endtask: get_dma_trans