uvm_analysis_port——TLM1事务级建模方法（二）

　　UVM中的TLM1端口，第一类是用于uvm_driver 和uvm_sequencer连接端口，第二类是用于其他component之间连接的端口，如uvm_monitor和uvm_scoreboard。首先让我们看第二类。首先来看uvm_analysis_port。

//------------------------------------------------------------------------------
// Title: Analysis Ports
//------------------------------------------------------------------------------
//
// This section defines the port, export, and imp classes used for transaction
// analysis.
//
//------------------------------------------------------------------------------


//------------------------------------------------------------------------------
// Class: uvm_analysis_port
//
// Broadcasts a value to all subscribers implementing a <uvm_analysis_imp>.
// 
//| class mon extends uvm_component;
//|   uvm_analysis_port#(trans) ap;
//|
//|   function new(string name = "sb", uvm_component parent = null);
//|      super.new(name, parent);
//|      ap = new("ap", this);
//|   endfunction
//|
//|   task run_phase(uvm_phase phase);
//|       trans t;
//|       ...
//|       ap.write(t);
//|       ...
//|   endfunction
//| endclass
//------------------------------------------------------------------------------

class uvm_analysis_port # (type T = int)
  extends uvm_port_base # (uvm_tlm_if_base #(T,T));

  function new (string name, uvm_component parent);
    super.new (name, parent, UVM_PORT, 0, UVM_UNBOUNDED_CONNECTIONS);
    m_if_mask = `UVM_TLM_ANALYSIS_MASK;  
  endfunction

  virtual function string get_type_name();
    return "uvm_analysis_port";
  endfunction

  // Method: write
  // Send specified value to all connected interface
  function void write (input T t);
    uvm_tlm_if_base # (T, T) tif;
    for (int i = 0; i < this.size(); i++) begin
      tif = this.get_if (i);
      if ( tif == null )
        uvm_report_fatal ("NTCONN", {"No uvm_tlm interface is connected to ", get_full_name(), " for executing write()"}, UVM_NONE);
      tif.write (t);
    end 
  endfunction

endclass



//------------------------------------------------------------------------------
// Class: uvm_analysis_imp
//
// Receives all transactions broadcasted by a <uvm_analysis_port>. It serves as
// the termination point of an analysis port/export/imp connection. The component
// attached to the ~imp~ class--called a ~subscriber~-- implements the analysis
// interface.
//
// Will invoke the ~write(T)~ method in the parent component.
// The implementation of the ~write(T)~ method must not modify
// the value passed to it.
//
//| class sb extends uvm_component;
//|   uvm_analysis_imp#(trans, sb) ap;
//|
//|   function new(string name = "sb", uvm_component parent = null);
//|      super.new(name, parent);
//|      ap = new("ap", this);
//|   endfunction
//|
//|   function void write(trans t);
//|       ...
//|   endfunction
//| endclass
//------------------------------------------------------------------------------

class uvm_analysis_imp #(type T=int, type IMP=int)
  extends uvm_port_base #(uvm_tlm_if_base #(T,T));
  `UVM_IMP_COMMON(`UVM_TLM_ANALYSIS_MASK,"uvm_analysis_imp",IMP)
  function void write (input T t);
    m_imp.write (t);
  endfunction
endclass



//------------------------------------------------------------------------------
// Class: uvm_analysis_export
//
// Exports a lower-level <uvm_analysis_imp> to its parent.
//------------------------------------------------------------------------------

class uvm_analysis_export #(type T=int)
  extends uvm_port_base #(uvm_tlm_if_base #(T,T));

  // Function: new
  // Instantiate the export.
  function new (string name, uvm_component parent = null);
    super.new (name, parent, UVM_EXPORT, 1, UVM_UNBOUNDED_CONNECTIONS);
    m_if_mask = `UVM_TLM_ANALYSIS_MASK;
  endfunction

  virtual function string get_type_name();
    return "uvm_analysis_export";
  endfunction
  
  // analysis port differs from other ports in that it broadcasts
  // to all connected interfaces. Ports only send to the interface
  // at the index specified in a call to set_if (0 by default).
  function void write (input T t);
    uvm_tlm_if_base #(T, T) tif;
    for (int i = 0; i < this.size(); i++) begin
      tif = this.get_if (i);
      if (tif == null)
         uvm_report_fatal ("NTCONN", {"No uvm_tlm interface is connected to ", get_full_name(), " for executing write()"}, UVM_NONE);
      tif.write (t);
    end 
  endfunction

endclass

我们可以看到所有的类都是继承自uvm_port_base #(uvm_tlm_if_base #(T,T))。uvm_analysis_imp其实更像一个普通的imp,它不具备有任何analysis的性质，即不具备任何广播的性质。对于uvm_analysis_port 和uvm_analysis_export 只能是analysis_imp.