Example of UVM hearbeat based on example and UVM heartbeat docs
Introduction Link to heading
UVM reference manual defines Heart Beat as
Heartbeats provide a way for environments to easily ensure that their descendants are alive. A uvm_heartbeat is associated with a specific objection object. A component that is being tracked by the heartbeat object must raise (or drop) the synchronizing objection during the heartbeat window. The synchronizing objection must be a uvm_callbacks_objection type.
which means a component can monitor a another component and expect “keep alive” objection in a given window. If we don’t receive signal, a fatal will be generated.
It’s useful to detect hanging component and make sure that specific tasks complete in a given window.
Step 1: create uvm_callbacks_object Link to heading
A objection object is shared by the environment and the component.
uvm_callbacks_objection obj = new("obj");
uvm_callbacks_object is defined as
The uvm_callbacks_objection is a specialized uvm_objection which contains callbacks for the raised and dropped events. Callbacks happend for the three standard callback activities, raised, dropped, and all_dropped.
which is not the same as uvm_objection_callback. Anyway, We won’t use callbacks raised and dropped and all_dropped in this example.
Step 2: Raise objections Link to heading
The run_phase(or whatever tasks consuming time) of component needs to periodically raise objection to obj.
task run_phase(uvm_phase phase);
repeat(10) begin
`uvm_info(get_type_name(),$sformatf("raise objections "),UVM_LOW)
obj.raise_objection(this);
// A delay is used to simulate time consuming tasks
[....]
end
Step 3: setup the environment Link to heading
according to UVM reference manual, we need to pass 2 things to uvm_heartbeat
- shared objection define above
uvm_eventto synchronize the window
we define heartbeat and event in env class
uvm_heartbeat hb = new("hb", this, obj);
uvm_event hb_event= new("hb_event");
Add the component to list monitored components. In this case, m_drv is component with heartbeat.
hb.add(m_drv);
Finally, hb needs to start by calling .start and passing the synchronization event hb_event.
In this example, i am defining a window of 100 units. If the m_drv doesn’t raise object in the window, the heartbeat will throw FATAL.
hb.start(hb_event);
repeat(10) begin
`uvm_info(get_type_name(),$sformatf("Triggering hb_event"),UVM_LOW)
hb_event.trigger();
#100;
end
Using #50 Link to heading
Using #50 means that driver will stop raising objections after 500 units. and the heatbeat will trigger at 500 and 600. And generates the FATAL message.
testbench.sv(54) @ 0: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 0: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(17) @ 50: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(54) @ 100: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 100: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(17) @ 150: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(54) @ 200: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 200: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(17) @ 250: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(54) @ 300: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 300: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(17) @ 350: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(54) @ 400: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 400: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(17) @ 450: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(54) @ 500: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(54) @ 600: uvm_test_top.m_env [env] Triggering hb_event
UVM_FATAL @ 600: uvm_test_top.m_env [HBFAIL] Did not recieve an update of obj for component uvm_test_top.m_env.m_drv since last event trigger at time 500 : last update time was 450
Using #100 Link to heading
Using #100 means that driver will raise objections in 100-unit window until the end of run_task where env stops triggering uvm_event. And simulation completes successfully.
testbench.sv(51) @ 0: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 0: uvm_test_top.m_env.m_drv [driver] raise objections
testbench.sv(51) @ 100: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 100: uvm_test_top.m_env.m_drv [driver] raise
testbench.sv(51) @ 200: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 200: uvm_test_top.m_env.m_drv [driver] raise
testbench.sv(51) @ 300: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 300: uvm_test_top.m_env.m_drv [driver] raise
testbench.sv(51) @ 400: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 400: uvm_test_top.m_env.m_drv [driver] raise
testbench.sv(51) @ 500: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 500: uvm_test_top.m_env.m_drv [driver] raise
testbench.sv(51) @ 600: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 600: uvm_test_top.m_env.m_drv [driver] raise
testbench.sv(51) @ 700: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 700: uvm_test_top.m_env.m_drv [driver] raise
testbench.sv(51) @ 800: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 800: uvm_test_top.m_env.m_drv [driver] raise
testbench.sv(51) @ 900: uvm_test_top.m_env [env] Triggering hb_event
testbench.sv(17) @ 900: uvm_test_top.m_env.m_drv [driver] raise objections
Putting all together Link to heading
`include "uvm_macros.svh"
import uvm_pkg::*;
uvm_callbacks_objection obj = new("obj");
class driver extends uvm_driver;
`uvm_component_utils(driver)
function new(string name="", uvm_component parent=null);
super.new(name, parent);
endfunction
task run_phase(uvm_phase phase);
repeat(10) begin
`uvm_info(get_type_name(),$sformatf("raise objections "),UVM_LOW)
obj.raise_objection(this);
#100;
end
endtask
endclass
class env extends uvm_env;
`uvm_component_utils(env)
driver m_drv;
uvm_heartbeat hb = new("hb", this, obj);
uvm_event hb_event= new("hb_event");
function new(string name="", uvm_component parent=null);
super.new(name, parent);
endfunction
function void build_phase(uvm_phase phase);
super.build_phase(phase);
m_drv = driver::type_id::create("m_drv", this);
endfunction
function void connect_phase(uvm_phase phase);
hb.add(m_drv);
endfunction
task run_phase(uvm_phase phase);
phase.raise_objection(this);
hb.start(hb_event);
repeat(10) begin
`uvm_info(get_type_name(),$sformatf("Triggering hb_event"),UVM_LOW)
hb_event.trigger();
#100;
end
#1000;
phase.drop_objection(this);
endtask
endclass
class test extends uvm_test;
`uvm_component_utils(test)
env m_env;
function new(string name="", uvm_component parent=null);
super.new(name, parent);
endfunction
function void build_phase(uvm_phase phase);
super.build_phase(phase);
m_env = env::type_id::create("m_env", this);
endfunction
task run_phase(uvm_phase phase);
phase.raise_objection(this);
`uvm_warning("Test","Hello World!")
phase.drop_objection(this);
endtask
endclass
module top;
initial run_test("test");
endmodule