UVM Tutorial for Candy Lovers – 21. TLM 1 Example

Keisuke Shimizu

In the previous post, we looked at an overview of the TLM 1 classes. This post will give you a sample code using some of the TLM 1 classes.

Components

We created the following components to demonstrate different kinds of TLM 1 interface. The jelly_bean_sequencer (the leftmost component) creates an object of the jelly_bean_transaction, called jb_req. The jb_req is transferred all the way to the right (jelly_bean_transporter) via several TLM 1 interfaces. The jelly_bean_transporter evaluates the flavor of the jb_req and returns another jelly_bean_transaction called jb_rsp (jelly-bean response) with the updated taste property. The jb_rsp is transferred back to the jelly_bean_subscriber at the end. Though this example is artificial, it will show you a variety of TLM 1 interfaces.

Sample TLM 1 Connections
Sample TLM 1 Connections

jelly_bean_sequencer

The jelly_bean_sequencer is a uvm_sequencer specialized with the jelly_bean_transaction.

typedef uvm_sequencer#(jelly_bean_transaction) jelly_bean_sequencer;

jelly_bean_put_driver

The jelly_bean_put_driver is a uvm_driver, which means it has a seq_item_port. The line 4 declares another port (put_port). The run_phase gets a jb_req from the seq_item_port (line 19) then puts it to the put_port (line 21).

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class jelly_bean_put_driver extends uvm_driver#( jelly_bean_transaction );
   `uvm_component_utils( jelly_bean_put_driver )
 
   uvm_put_port#( jelly_bean_transaction ) put_port; 
   function new( string name, uvm_component parent );
      super.new( name, parent );
   endfunction: new
 
   function void build_phase( uvm_phase phase );
      super.build_phase( phase );
      put_port = new( .name( "put_port" ), .parent( this ) );
   endfunction: build_phase
 
   task run_phase( uvm_phase phase );
      jelly_bean_transaction jb_req;
 
      forever begin
         seq_item_port.get_next_item( jb_req );         `uvm_info( get_type_name(), "[seq_item_port]-->{jb_req}-->[put_port]", UVM_NONE )
         put_port.put( jb_req );         seq_item_port.item_done();
      end
   endtask: run_phase
endclass: jelly_bean_put_driver

jelly_bean_master

The jelly_bean_master has one uvm_get_port (get_port, line 4), one uvm_master_port (master_port, lines 5 and 6), and one uvm_analysis_port (rsp_ap, line 7). The run_phase gets a jb_req from the get_port (line 25), then puts it to the master_port (line 27). The jelly_bean_master waits for a jelly-bean response (jb_rsp, line 29), then writes it to the rsp_ap (line 31).

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class jelly_bean_master extends uvm_component;
   `uvm_component_utils( jelly_bean_master )
 
   uvm_get_port#( jelly_bean_transaction ) get_port;   uvm_master_port#( .REQ( jelly_bean_transaction ),                      .RSP( jelly_bean_transaction ) ) master_port;   uvm_analysis_port#( jelly_bean_transaction ) rsp_ap; 
   function new( string name, uvm_component parent );
      super.new( name, parent );
   endfunction: new
 
   function void build_phase( uvm_phase phase );
      super.build_phase( phase );
      get_port    = new( .name( "get_port" ),    .parent( this ) );
      master_port = new( .name( "master_port" ), .parent( this ) );
      rsp_ap      = new( .name( "rsp_ap" ),      .parent( this ) );
   endfunction: build_phase
 
   task run_phase( uvm_phase phase );
      jelly_bean_transaction jb_req;
      jelly_bean_transaction jb_rsp;
 
      forever begin
         get_port.get( jb_req );         `uvm_info( get_type_name(), "[get_port]-->{jb_req}-->[master_port]", UVM_NONE )
         master_port.put( jb_req );         `uvm_info( get_type_name(), "{jb_rsp}< --[master_port]", UVM_NONE )
         master_port.get( jb_rsp );         `uvm_info( get_type_name(), "{jb_rsp}-->[rsp_ap]", UVM_NONE )
         rsp_ap.write( jb_rsp );      end
   endtask: run_phase
endclass: jelly_bean_master

jelly_bean_slave

The jelly_bean_slave has one uvm_master_imp (master_export, lines 4 to 6), and one uvm_transport_port (trans_port, lines 7 and 8). The jelly_bean_slave also has two queues; the req_q stores the jb_reqs and the rsp_q stores the jb_rsps. The jelly_bean_slave implements the access methods of a uvm_master_imp; namely put, try_put, can_put, get, try_get, can_get, peek, try_peek, and can_peek (lines 34 to 81). The run_phase gets a jb_req from the req_q if available, then calls transport of the trans_port (line 28).

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class jelly_bean_slave extends uvm_component;
   `uvm_component_utils( jelly_bean_slave )
 
   uvm_master_imp#( .REQ( jelly_bean_transaction ),                     .RSP( jelly_bean_transaction ),                    .IMP( jelly_bean_slave ) ) master_export;   uvm_transport_port#( .REQ( jelly_bean_transaction ),                        .RSP( jelly_bean_transaction ) ) trans_port;   jelly_bean_transaction req_q[$];
   jelly_bean_transaction rsp_q[$];
 
   function new( string name, uvm_component parent );
      super.new( name, parent );
   endfunction: new
 
   function void build_phase( uvm_phase phase );
      super.build_phase( phase );
      master_export = new( "master_export", this );
      trans_port    = new( .name( "trans_port" ), .parent( this ) );
   endfunction: build_phase
 
   task run_phase( uvm_phase phase );
      jelly_bean_transaction jb_rsp;
 
      forever begin
         wait ( req_q.size() > 0 );
         `uvm_info( get_type_name(), "(master_export)---{jb_req}-->[trans_port]", UVM_NONE )
         trans_port.transport( req_q.pop_front(), jb_rsp );         `uvm_info( get_type_name(), "{jb_rsp}< --[trans_port]", UVM_NONE )
         rsp_q.push_back( jb_rsp );
      end
   endtask: run_phase
 
   virtual task put( input jelly_bean_transaction t );
      req_q.push_back( t );
   endtask: put
 
   virtual function bit try_put( input jelly_bean_transaction t );
      req_q.push_back( t );
      return 1;
   endfunction: try_put
 
   virtual function bit can_put();
      return 1;
   endfunction: can_put
 
   virtual task get( output jelly_bean_transaction t );
      wait ( rsp_q.size() > 0 );
      t = rsp_q.pop_front();
   endtask: get
 
   virtual function bit try_get( output jelly_bean_transaction t );
      if ( rsp_q.size() > 0 ) begin
         t = rsp_q.pop_front();
         return 1;
      end else begin
         return 0;
      end
   endfunction: try_get
 
   virtual function bit can_get();
      return rsp_q.size() > 0;
   endfunction: can_get
 
   virtual task peek( output jelly_bean_transaction t );
      wait ( rsp_q.size() > 0 );
      t = rsp_q[0];
   endtask: peek
 
   virtual function bit try_peek( output jelly_bean_transaction t );
      if ( rsp_q.size() > 0 ) begin
         t = rsp_q[0];
         return 1;
      end else begin
         return 0;
      end
   endfunction: try_peek
 
   virtual function bit can_peek();
      return rsp_q.size() > 0;
   endfunction: can_peek
endclass: jelly_bean_slave

jelly_bean_transporter

The jelly_bean_transporter has one uvm_transport_imp (trans_export, lines 4 to 6) and implements its access methods; namely transport and nb_transport (lines 17 to 32). These methods create a jelly-bean response (jb_rsp, line 24), evaluate the flavor of a jelly-bean request and update the taste property of the jb_rsp accordingly (lines 26 to 29).

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class jelly_bean_transporter extends uvm_component;
   `uvm_component_utils( jelly_bean_transporter )
 
   uvm_transport_imp#( .REQ( jelly_bean_transaction ),                       .RSP( jelly_bean_transaction ),                       .IMP( jelly_bean_transporter ) ) trans_export; 
   function new( string name, uvm_component parent );
      super.new( name, parent );
   endfunction: new
 
   function void build_phase( uvm_phase phase );
      super.build_phase( phase );
      trans_export = new( "trans_export", this );
   endfunction: build_phase
 
   virtual task transport( input  jelly_bean_transaction jb_req,
                           output jelly_bean_transaction jb_rsp );
      assert( nb_transport( jb_req, jb_rsp ) );
   endtask: transport
 
   virtual function bit nb_transport( input  jelly_bean_transaction jb_req,
                                      output jelly_bean_transaction jb_rsp );
      jb_rsp = jelly_bean_transaction::type_id::create( "jb_rsp" );      jb_rsp.copy( jb_req );
      if ( jb_req.flavor == jelly_bean_transaction::CHOCOLATE && jb_req.sour )        jb_rsp.taste = jelly_bean_transaction::YUCKY;      else        jb_rsp.taste = jelly_bean_transaction::YUMMY;      `uvm_info( get_type_name(), { "Returning:\n", jb_rsp.sprint() }, UVM_NONE )
      return 1;
   endfunction: nb_transport
endclass: jelly_bean_transporter

jelly_bean_subscriber

The jelly_bean_subscriber is a uvm_subscriber, which means it has an analysis_export. The jelly_bean_subscriber implements the write method of the analysis_export (lines 8 to 10).

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class jelly_bean_subscriber extends uvm_subscriber#( jelly_bean_transaction );
   `uvm_component_utils( jelly_bean_subscriber )
 
   function new( string name, uvm_component parent );
      super.new( name, parent );
   endfunction: new
 
   function void write( jelly_bean_transaction t );      `uvm_info( get_type_name(), { "Received:\n", t.sprint() }, UVM_NONE )   endfunction: writeendclass: jelly_bean_subscriber

jelly_bean_agent

The jelly_bean_agent instantiates all the components and connect them together.

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class jelly_bean_agent extends uvm_agent;
   `uvm_component_utils( jelly_bean_agent )
 
   jelly_bean_sequencer                    jb_seqr;
   jelly_bean_put_driver                   jb_put_drvr;
   uvm_tlm_fifo#( jelly_bean_transaction ) jb_fifo;
   jelly_bean_master                       jb_master;
   jelly_bean_slave                        jb_slave;
   jelly_bean_transporter                  jb_trans;
   jelly_bean_subscriber                   jb_sub;
 
   function new( string name, uvm_component parent );
      super.new( name, parent );
   endfunction: new
 
   function void build_phase( uvm_phase phase );
      super.build_phase( phase );
      jb_seqr     = jelly_bean_sequencer  ::type_id::create( .name( "jb_seqr" ),     .parent( this ) );
      jb_put_drvr = jelly_bean_put_driver ::type_id::create( .name( "jb_put_drvr" ), .parent( this ) );
      jb_fifo     = new(                                     .name( "jb_fifo" ),     .parent( this ) );
      jb_master   = jelly_bean_master     ::type_id::create( .name( "jb_master" ),   .parent( this ) );
      jb_slave    = jelly_bean_slave      ::type_id::create( .name( "jb_slave" ),    .parent( this ) );
      jb_trans    = jelly_bean_transporter::type_id::create( .name( "jb_trans" ),    .parent( this ) );
      jb_sub      = jelly_bean_subscriber ::type_id::create( .name( "jb_sub" ),      .parent( this ) );
   endfunction: build_phase
 
   function void connect_phase( uvm_phase phase );
      super.connect_phase( phase );
      jb_put_drvr.seq_item_port.connect( jb_seqr.seq_item_export );
      jb_put_drvr.     put_port.connect( jb_fifo.put_export );
      jb_master.       get_port.connect( jb_fifo.get_peek_export );
      jb_master.    master_port.connect( jb_slave.master_export );
      jb_slave.      trans_port.connect( jb_trans.trans_export );
      jb_master.         rsp_ap.connect( jb_sub.analysis_export );
   endfunction: connect_phase
endclass: jelly_bean_agent

Simulation

Here is an excerpt of a simulation output.

# UVM_INFO ../src/tutorial_20.sv(118) @ 0: uvm_test_top.jb_env.jb_agent.jb_seqr@@jb_seq [one_jelly_bean_sequence] Generated:
# UVM_INFO ../src/tutorial_20.sv(152) @ 0: uvm_test_top.jb_env.jb_agent.jb_put_drvr [jelly_bean_put_driver] [seq_item_port]-->{jb_req}-->[put_port]
# UVM_INFO ../src/tutorial_20.sv(188) @ 0: uvm_test_top.jb_env.jb_agent.jb_master [jelly_bean_master] [get_port]-->{jb_req}-->[master_port]
# UVM_INFO ../src/tutorial_20.sv(223) @ 0: uvm_test_top.jb_env.jb_agent.jb_slave [jelly_bean_slave] (master_export)---{jb_req}-->[trans_port]
# UVM_INFO ../src/tutorial_20.sv(282) @ 0: uvm_test_top.jb_env.jb_agent.jb_trans [jelly_bean_transporter] Returning:
# UVM_INFO ../src/tutorial_20.sv(225) @ 0: uvm_test_top.jb_env.jb_agent.jb_slave [jelly_bean_slave] {jb_rsp}< --[trans_port]
# UVM_INFO ../src/tutorial_20.sv(190) @ 0: uvm_test_top.jb_env.jb_agent.jb_master [jelly_bean_master] {jb_rsp}<--[master_port]
# UVM_INFO ../src/tutorial_20.sv(192) @ 0: uvm_test_top.jb_env.jb_agent.jb_master [jelly_bean_master] {jb_rsp}-->[rsp_ap]
# UVM_INFO ../src/tutorial_20.sv(298) @ 0: uvm_test_top.jb_env.jb_agent.jb_sub [jelly_bean_subscriber] Received:

I hope this tutorial helped you to understand the TLM 1 interfaces.

Get source code

9 thoughts on “UVM Tutorial for Candy Lovers – 21. TLM 1 Example”

  1. Hi Keisuke:
    great Tutorial and very helpful.
    Is there any possibility to post anything about callback, like recommand usage, work mode etc, very appreciated
    Thanks. Pan

    Reply

    1. Thanks for the comment. UVM does provide a callback mechanism, but it is not recommended to use due to a performance impact. I would suggest to use the UVM factory to override a class instead of using a callback.

      Reply

  2. Hi Keisuke,

    Whats the difference between imp and export ?? Practical use of each of them ?? Thanks in advance………

    Reply

  3. Thanks for the tutorial. I have what I need now to build a very powerful environment for data cache verification.

    Reply

  4. In your example, you connect get_peek_export to get_port (not get_peek_port) from uvm_tlm_fifo to jelly_bean_master. Is it because get_port is just a subset of get_peek_port, that is why we can use get_port here?

    Reply

    1. That’s right. While get_peek_export implements get, try_get, can_get, peek, try_peek, and can_peek, get_port implements get, try_get, and can_get only. Since all the methods the consumer (jelly_bean_master) can call via its get_port are supported by the get_peek_export, you can connect them together.

      Reply

  5. Hi Keisuke,
    I noticed that when you implement the access methods of a uvm_master_imp in jelly_bean_slave, some methods you use functions to realize, some methords you use tasks, for example, the put method you use task, while the try_put method you use function.
    I wonder to know why you choose task on some methods and funciton on others?
    Thanks,
    Rui

    Reply

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