Components Link to heading

UVM defines set of standard building blocks to build test hierarchy. All components inherit from uvm_component. but some components have more bells and whistles than others.

uvm_comps.svh Link to heading

starting with src/comps/uvm_comps.svh where components live, we can see there are two types

  • Utility components
  • Structural components
 `include "comps/uvm_pair.svh"
 `include "comps/uvm_policies.svh"
 `include "comps/uvm_in_order_comparator.svh"
 `include "comps/uvm_algorithmic_comparator.svh"
 `include "comps/uvm_random_stimulus.svh"
 `include "comps/uvm_subscriber.svh"

 `include "comps/uvm_monitor.svh"
 `include "comps/uvm_driver.svh"
 `include "comps/uvm_push_driver.svh"
 `include "comps/uvm_scoreboard.svh" 
 `include "comps/uvm_agent.svh"
 `include "comps/uvm_env.svh"
 `include "comps/uvm_test.svh"

The vanilla components Link to heading

There are several components which are just extension of uvm_component without adding any further functionality.

for example uvm_env

virtual class uvm_env extends uvm_component;

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

  const static string type_name = "uvm_env";

  virtual function string get_type_name ();
    return type_name;
  endfunction

endclass

The list of wrapper components are

  • uvm_env
  • uvm_monitor
  • uvm_scoreboard
  • uvm_test

That said, There are two components that add attributes to base uvm_component

  • uvm_driver
  • uvm_agent

uvm_driver Link to heading

uvm_driver adds seq_item_port for sequencer connection.

  uvm_seq_item_pull_port #(REQ, RSP) seq_item_port;

  uvm_seq_item_pull_port #(REQ, RSP) seq_item_prod_if; // alias

  uvm_analysis_port #(RSP) rsp_port;

and new

  function new (string name, uvm_component parent);
    super.new(name, parent);
    seq_item_port    = new("seq_item_port", this);
    rsp_port         = new("rsp_port", this);
    seq_item_prod_if = seq_item_port;
  endfunction // new

To go off on a tangent here, I wanted to know what seq_item_prod_if is. Grep’ing through ‘src’, I found it in ovm2uvm.pl which indicated it was deprecated ovm artifact. Quick look at OVM specs and i confirmed it.

    # FIX+MARKER seq_item_prod_if -> seq_item_port
    $t =~ s/seq_item_prod_if.*/$& \/\/ $opt_marker NOTE seq_item_prod_if has been replaced with seq_item_port \n/g;
    $t =~ s/seq_item_prod_if/seq_item_port/g;

uvm_agent Link to heading

uvn_agent adds only one attribute is_active to mark agent as active or passive.

  uvm_active_passive_enum is_active = UVM_ACTIVE;

is_active is set by setting is_active in uvm_config with specific path of that agent.

there is also get_is_active which returns the current value.

  function void build_phase(uvm_phase phase);
    int active;
    super.build_phase(phase);
    if(get_config_int("is_active", active)) is_active = uvm_active_passive_enum'(active);
  endfunction

  // the active/passive nature of the agent.

  virtual function uvm_active_passive_enum get_is_active();
    return is_active;
  endfunction