Layered Sequence

// Upper-layer classes

class upper_item extends uvm_sequence_item;

    ...

endclass : upper_item

class upper_sequencer extends uvm_sequencer #(upper_item);

    ...

endclass : upper_sequencer

// Lower-layer classes

class lower_item extends uvm_sequence_item;

    ...

endclass : lower_item

class lower_sequencer extends uvm_sequencer #(lower_item);

    uvm_seq_item_pull_port #(upper_item) upper_seq_item_port;

    ...

    function new (string name, uvm_component parent);

        super.new(name, parent);

        upper_seq_item_port = new(“upper_seq_item_port”,this);

    endfunction : new

    ...

endclass : lower_sequencer

class lower_driver extends uvm_driver #(lower_item);

    ...

endclass : lower_driver

class higher_to_lower_seq extends uvm_sequence #(lower_item);

    ... // Constructor and UVM automation macros go here.

    // See Section 4.8.2

    upper_item u_item;

    lower_item l_item;

    virtual task body();

        forever begin

            `uvm_do_with(l_item,

            { ... }) // Constraints based on u_item

        end

    endtask : body

    // In the pre_do task, pull an upper item from upper sequencer.

    virtual task pre_do(bit is_item);

        p_sequencer.upper_seq_item_port.get_next_item(u_item);

    endtask : pre_do

    // In the post_do task, signal the upper sequencer we are done.

    // And, if desired, update the upper-item properties for the

    // upper-sequencer to use.

    virtual function void post_do(uvm_sequence_item this_item);

        p_sequencer.upper_seq_item_port.item_done(this_item);

    endfunction : post_do

endclass : higher_to_lower_seq