OVM 101 - part 2.

Test Environment Nitty Gritty Code

• Configuration - Connecting virtual interface from top level to DUT.
• Use configuration table to store the wrapper(s) of virtual interface properties.
• This way, the test bench can be used with different configurations, changing wrappers.
• Configuration using "set_config_object" and "get_config_object" overrides top-down.
  ( from ovm_test -> ovm_env -> ovm_component)

// Top level "module" contains class based test environment
//        and structural interface that drives DUT (module)
module top;

import ovm_pkg::*;
import my_pkg::*;

...
dut_if dut_if_inst1 ();
dut dut_inst0 (._if (dut_if_inst1) );

initial begin: blk
    dut_if_wrapper if_wrapper = new ("if_wrapper", dut_if_inst1);
                   // path  field_name        value      0: don't clone
    set_config_object("*", "dut_if_wrapper", if_wrapper, 0);

    run_test ("my_test_set");
end

endmodule : top

class dut_if_wrapper extends ovm_object;

    virtual dut_if dut_vi;
    function new (string s, virtual dut_if if_arg); 
        super.new(s);
        dut_vi = if_arg;
    endfunction : new

endclass : dut_if_wrapper

// ovm classes
// usually classes of test environment that includes fixed test bench
// and variable test sets

`include "ovm_macros.svh"

package my_package;
import ovm_pkg::*;

// Fixed test environment
class my_test_env extends ovm_env;
    `ovm_component_utils (my_test_env)

    virtual dut_if dut_virtual_if_inst;

    // constructor
    function new (string s, ovm_component inst_parent);
        super.new (s, inst_parent);
    endfunction : new

    function void build;
        super.build ();
        begin
            ovm_object obj;
            dut_if_wrapper if_wrapper; 
            get_config_object("dut_if_wrapper", obj, 0);
            assert( $cast(if_wrapper, obj) );
            dut_virtual_if_inst = if_wrapper.dut_vi;
        end
    endfunction : build

    task run;
        #10 dut_virtual_if_inst.data = 0;
        #10 dut_virtual_if_inst.data = 1;
        #10 ovm_top.stop_request();
    endtask : run

endclass : my_test_env

class my_test_set extends ovm_test;
    `ovm_component_utils (my_test_set)

    my_test_env my_test_env_handle;

    // constructor
    function new(string s, ovm_component inst_parent);
        super.new(s, inst_parent);
    endfunction : new

    function void build;
        super.build();
        my_test_env_handle = my_test_env::type_id::create
            ("my_test_env_handle", this);
    endfunction : build

endclass : my_test_set

// interface dut_if(); -> between test components and DUT
interface dut_if ();

    logic clock, reset;
    logic data_input;

endinterface : dut_if

// Design under test
module DUT (dut_if _if);

    always @ (posedge _if.clock)
    begin
    end

endmodule : dut

// Higher level overriding lower level configuration
// Overriding Example:
// in ovm_test
set_config_object ("*", "data", x);
// in ovm_env
get_config_object ("opt", y);
set_config_object ("*", "data", y);
// in ovm_component
get_config_object ("data", obj); // obj = x