In reply to Prawin kumar:
REQ, RSP are the type parameters of uvm_driver #(REQ,RSP) and uvm_sequencer #(REQ,RSP) components and its default type is uvm_sequence_item (please check the uvm_driver.svh code below). When you derive your own driver and sequencer from uvm_driver and uvm_sequencer, you can pass your sequence item type such as “seq_item” as you mentioned to replace the default one.
For example:
class my_driver extends uvm_driver #(seq_item);
This will automatically replace all REQ, RSP type as “seq_item” type for seq_item_port, seq_item_prod_if, rsp_port, req and rsp declarations of uvm_driver. You can use these built-in data and ports directly, don’t need to re-declare as they are already in uvm_driver for use.
typedef class uvm_sequence_item;
//------------------------------------------------------------------------------
//
// CLASS: uvm_driver #(REQ,RSP)
//
// The base class for drivers that initiate requests for new transactions via
// a uvm_seq_item_pull_port. The ports are typically connected to the exports of
// an appropriate sequencer component.
//
// This driver operates in pull mode. Its ports are typically connected to the
// corresponding exports in a pull sequencer as follows:
//
//| driver.seq_item_port.connect(sequencer.seq_item_export);
//| driver.rsp_port.connect(sequencer.rsp_export);
//
// The ~rsp_port~ needs connecting only if the driver will use it to write
// responses to the analysis export in the sequencer.
//
//------------------------------------------------------------------------------
class uvm_driver #(type REQ=uvm_sequence_item,
type RSP=REQ[/b]) extends uvm_component;
// Port: seq_item_port
//
// Derived driver classes should use this port to request items from the
// sequencer. They may also use it to send responses back.
uvm_seq_item_pull_port #(REQ, RSP) seq_item_port;
uvm_seq_item_pull_port #(REQ, RSP) seq_item_prod_if; // alias
// Port: rsp_port
//
// This port provides an alternate way of sending responses back to the
// originating sequencer. Which port to use depends on which export the
// sequencer provides for connection.
uvm_analysis_port #(RSP) rsp_port;
REQ req;
RSP rsp;
// Function: new
//
// Creates and initializes an instance of this class using the normal
// constructor arguments for <uvm_component>: ~name~ is the name of the
// instance, and ~parent~ is the handle to the hierarchical parent, if any.
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
const static string type_name = "uvm_driver #(REQ,RSP)";
virtual function string get_type_name ();
return type_name;
endfunction
endclass