UVM: TLM Interfaces (Ports, Exports, FIFOs)

Prod/Consumer example - put

• This example is about how two components can communicate on a TLM channel by using some of the TLM interface methods.
• So, let us say a producer wants to produce information or the consumer wants to consume the transactions. Thus, there are 2 ways in which producer and consumer can transfer the info between producer and consumer.
• First: the producer is doing a put into the consumer.
• Second: the consumer gets or pulls from the producer and gets info directly into itself.
• Example code:

class producer extends uvm_component;

 uvm_blocking_put_port #() put_port; //1 parameter

 function new(string name, uvm_component parent);

  put_port = new("put_port", this);

...

 endfunction

 virtual task run();

  simple_trans t;

  for(int i = 0; i < N; i++) begin

   //Generate t.

   put_port.put(t);

  end

 endtask

Example on the consumer (put port):

----------------------------------------

class consumer extends uvm_component;

 uvm_blocking_put_imp #(simple_trans, consumer) put_export;

 ...

 task put (simple_trans t);

  case(t.kind)

   READ: //Do read.

   WRITE: //Do Write.

  endcase

 endtask

endclass

Prod/Consumer example - get

class get_consumer extends uvm_consumer;

 uvm_blocking_get_port #() get_port;

 function new(string name, uvm_component parent);

   get_port = new("get_port", this);

...

 endfunction

 virtual task run();

   simple_trans t;

   for(int i = 0; i < N; i++) begin

    //Generate t.

    get_port.get(t);

   end

  endtask

---------------------------------------

class get_producer extends uvm_component;

 uvm_blocking_get_imp #(simple_trans, get_producer) get_export;

 ...

 task get(output simple_trans t);

  simple_trans tmp = new();

  //Assign values to tmp.

 t = tmp;

  endtask

 endclass

TLM FIFO Channel:

• Multiple transactions to be communicated.
• The producer need not wait until the consumer consumes each transaction.
• TLM FIFO (uvm_tlm_fifo) will have get/port functionality.
• one-to-one connection - connect two components.

Connecting Producer to Consumer:

class my_env extends uvm_env;

 ...

 virtual function void connect();

  // component.port.connect(target.export);

  producer.blocking_put_port.connect(fifo.put_export);

  get_consumer.get_port.connect(fifo.get_export);

 ...

 endfunction

endclass

Analysis Ports:

• Analysis ports support 1: many connections (uvm_analysis_port)
• Used by coverage collectors and score boards.
• The analysis port contains a list of analysis_exports that are connected to it.
• When the component calls analysis_port.write(), theanalysis_port cycles through the list and calls the write() method of each connected export.

class my_env extends uvm_env;

   get_ap_component g;

   sub1 s1;

   sub2 s2;

 ...

 function void connect();

    g.ap.connect(s1.analysis_export);

    g.ap.connect(s2.analysis_export);

    ...

   endfunction

endclass

• Analysis Ports: Used for communication between one component to multiple components (typically to broadcast info).

• Analysis FIFOs: Extended from TLM FIFO
• It provides an "implementation" style export.
• The implementation of "write" will place the date into a FIFO.

Example:

FIG: Example usage of Analysis Ports and FIFOs

General points to know on TLM:

1. A transaction is a class object that abstracts some information to be communicated between two components.

2. "write()" TLM interface is a non-blocking task.

3. Difference between a TLM port and Analysis port: Analysis port supports 1 to many connections while TLM ports support only one to one connections.