UVM/uvm-1.2/docs/html/src/overviews/test-phasing.txt

Title: User-Defined Phases

To define your own custom phase, use the following pattern.

 1. Extend the appropriate base class for your phase type.
|       class my_PHASE_phase extends uvm_task_phase;
|       class my_PHASE_phase extends uvm_topdown_phase;
|       class my_PHASE_phase extends uvm_bottomup_phase;

 2. Optionally, implement your exec_task or exec_func method.
|       task exec_task(uvm_component comp, uvm_phase schedule);
|       function void exec_func(uvm_component comp, uvm_phase schedule);

    If implemented, these methods usually call the related method on the component
|          comp.PHASE_phase(uvm_phase phase);

 3. Since the phase class is a singleton, providing an accessor method allows
    for easy global use, and protecting the constructor prevents misuse.
|       class my_PHASE_phase extends uvm_topdown_phase;  or uvm_task_phase/uvm_bottomum_phase
|         static local my_PHASE_phase m_inst;      Local reference to global IMP 
|         protected function new(string name="PHASE");    Protected constructor for singleton
|           super.new(name);
|         endfunction : new
|         static function my_PHASE_phase get();   Static method for accessing singleton
|           if (m_imp == null)
|             m_imp = new();
|           return m_imp;
|         endfunction : get
|          Optionally implement exec_func/exec_task
|       endclass : my_PHASE_phase

 4. Insert the phase in a phase schedule or domain using the
    <uvm_phase::add> method:
|       my_schedule.add(my_PHASE_class::get());