usage of get_trigger_data()

[Mital]

Hi All,
I am facing the following issue while using get_trigger_data() to get the data associated with the last trigger event.

When I use get_trigger_data(), after wait_trigger(), I am getting the correct value of data. Now, I change the field of packet "data2.sfd =1". After this, I am again calling get_trigger_data() in other task. Then why the updated value of sfd is displayed? According to the functionality, get_trigger_data() should reflect the data associated with a last trigger event.

I have tried the following code:


import ovm_pkg::*;
`include "ovm_macros.svh"

class packet extends ovm_sequence_item;
rand bit [7:0] sfd;
`ovm_object_utils_begin(packet)
`ovm_field_int(sfd, OVM_ALL_ON)
`ovm_object_utils_end
function new (string name = "packet");
super.new(name);
endfunction : new
endclass: packet

class bfm_c extends ovm_driver;
packet data1;
packet data2;
packet data3;
ovm_object datax;
ovm_object datax1;
ovm_event ack_process;
`ovm_component_utils(bfm_c)

function new(string name ="", ovm_component parent);
super.new(name, parent);
ack_process = new("ack");
data1 = new("data1");
data2 = new("data2");
data3 = new("data3");
endfunction

task run;
fork
begin #1;
ack_process.wait_trigger();
datax = ack_process.get_trigger_data();
$cast(data2,datax);
$display("After wait data2.sfd=%d", data2.sfd);
data2.sfd=1;
end
begin #4;
void'(data1.randomize());
ack_process.trigger(data1);
end
join
task_1();
endtask

task task_1;
begin
datax1 = ack_process.get_trigger_data();
$cast(data3,datax1);
$display("data3.sfd=%d", data3.sfd);
end
endtask
endclass : bfm_c

module top;
bfm_c e;
initial begin e = new("bfm_c",null); run_test();
end
endmodule


Is this the expected behaviour of get_trigger_data()? Please let me know about this.

Thanks,
Mital

[dlong]

Hi Mital,

ack_process.get_trigger_data() returns a class handle. $cast copies the class handle to your data2 variable. Anything you do to data2 is actually being done to the object you originally passed into the ovm_event via the call to trigger.

If you want to modify data2 without changing the ovm_event data you should copy or clone the returned object, e.g.



$cast( data2,datax.clone() );


Regards,
Dave