Raise/Drop objection Automatically with UVM
Variable uvm_sequence_base::starting_phase is deprecated and replaced by two new methods set_starting_phase and get_starting_phase, which prevent starting_phase from being modified in the middle of a phase. This change is not backward-compatible with UVM 1.1, though variable starting_phase, although deprecated, has not yet been removed from the base class library.
New method uvm_sequence_base::set_automatic_phase_objection causes raise_objection and drop_objection to be called automatically around a sequence, avoiding the need to call raise/drop_objection manually in one common situation.
Lets understand it through below mentioned example.
import uvm_pkg :: *;
class my_seq_item extends uvm_sequence_item;
rand logic [7:0] addr;
rand logic [7:0] data;
constraint addr_range_cn {
addr inside {[10:20]};
}
constraint data_range_cn {
data inside {[100:200]};
}
`uvm_object_utils_begin(my_seq_item)
`uvm_field_int(addr, UVM_ALL_ON| UVM_DEC)
`uvm_field_int(data, UVM_ALL_ON| UVM_DEC)
`uvm_object_utils_end
function new(string name="my_seq_item");
super.new(name);
endfunction : new
virtual function string convert2string();
convert2string = $sformatf("addr=%0d, data=%0d", addr, data);
endfunction : convert2string
endclass : my_seq_item
class my_sequencer extends uvm_sequencer #(my_seq_item);
`uvm_component_utils (my_sequencer)
function new (string name="my_sequencer", uvm_component parent=null);
super.new(name, parent);
endfunction : new
endclass : my_sequencer
class my_driver extends uvm_driver #(my_seq_item);
`uvm_component_utils (my_driver)
function new (string name="my_driver", uvm_component parent=null);
super.new(name, parent);
endfunction : new
function void build_phase (uvm_phase phase);
super.build_phase(phase);
endfunction : build_phase
task run_phase(uvm_phase phase);
forever begin
seq_item_port.get_next_item(req);
`uvm_info(get_name(),
$sformatf("in driver after get_next_item my_seq_item= %s", req.convert2string()), UVM_LOW);
#50;
`uvm_info(get_name(), $sformatf("item_done called"), UVM_LOW);
seq_item_port.item_done();
end
endtask : run_phase
endclass : my_driver
class my_agent extends uvm_agent;
`uvm_component_utils (my_agent)
my_sequencer sqr;
my_driver drv;
function new (string name="my_agent", uvm_component parent=null);
super.new(name, parent);
endfunction : new
function void build_phase (uvm_phase phase);
super.build_phase(phase);
sqr = my_sequencer :: type_id :: create("sqr", this);
drv = my_driver :: type_id :: create("drv", this);
endfunction : build_phase
function void connect_phase (uvm_phase phase);
super.connect_phase(phase);
drv.seq_item_port.connect(sqr.seq_item_export);
endfunction : connect_phase
endclass : my_agent
class my_seq extends uvm_sequence #(my_seq_item);
`uvm_object_utils (my_seq)
function new(string name="my_seq");
super.new(name);
// The most common interaction with the starting phase
// within a sequence is to simply RAISE the phase's objection
// prior to executing the sequence, and DROP the objection
// after ending the sequence (either naturally, or
// via a call to <kill>). In order to
// simplify this interaction for the user, the UVM
// provides the ability to perform this functionality
// automatically.
// From a timeline point of view, the automatic phase objection
// looks like:
//| start() is executed
//| --! Objection is raised !--
//| pre_start() is executed
//| pre_body() is optionally executed
//| body() is executed
//| post_body() is optionally executed
//| post_start() is executed
//| --! Objection is dropped !--
//| start() unblocks
// NEVER set the automatic phase objection bit to 1 if your sequence
// runs with a forever loop inside of the body, as the objection will
// never get dropped!
set_automatic_phase_objection(1);
endfunction : new
task body ();
`uvm_create(req)
if(!req.randomize()) begin
`uvm_fatal(get_name(), $sformatf("Randomization failed"))
end
`uvm_info (get_name(),
$sformatf("After randomizating in my_seq my_seq_item= %s",
req.convert2string()), UVM_LOW)
`uvm_send(req)
endtask : body
endclass : my_seq
class my_test extends uvm_test;
`uvm_component_utils (my_test)
my_agent agent;
function new (string name="my_test", uvm_component parent=null);
super.new(name, parent);
endfunction : new
function void build_phase (uvm_phase phase);
super.build_phase(phase);
agent = my_agent::type_id::create("agent", this);
endfunction : build_phase
task run_phase(uvm_phase phase);
my_seq seq;
uvm_phase starting_phase;
bit automatic_phase_objection_status;
seq = my_seq::type_id::create ("seq");
// Function: set_starting_phase
// Sets the 'starting phase'.
seq.set_starting_phase(phase);
// If set_automatic_phase_objection is not called in new (constructor)
// of sequence then can be calleb from test-case
// seq.set_automatic_phase_objection(1);
fork
begin
#30;
// Function: get_starting_phase
// Returns the 'starting phase'.
// If non-null, the starting phase specifies the phase in which this
// sequence was started.
starting_phase = seq.get_starting_phase();
`uvm_info(get_name(),
$sformatf("starting_phase:%s", starting_phase.get_full_name()), UVM_LOW)
// Function: get_automatic_phase_objection
// Returns (and locks) the value of the 'automatically object to
// starting phase' bit.
//
// If 1, then the sequence will automatically raise an objection
// to the starting phase (if the starting phase is not NULL) immediately
// prior to <pre_start> being called. The objection will be dropped
// after <post_start> has executed, or <kill> has been called.
automatic_phase_objection_status = seq.get_automatic_phase_objection();
`uvm_info(get_name(),
$sformatf("during seq is running, get_automatic_phase_objection returns :%b", automatic_phase_objection_status), UVM_LOW)
end
join_none
seq.start(agent.sqr);
automatic_phase_objection_status = seq.get_automatic_phase_objection();
`uvm_info(get_name(),
$sformatf("After seq finished, get_automatic_phase_objection returns :%b", automatic_phase_objection_status), UVM_LOW)
endtask : run_phase
endclass : my_test
module top();
initial begin
run_test("my_test");
end
endmodule : top
