下列这段程序能实现的功能为（        ）。
begin
        PrevPwm <= PwmControl    

if (PwmControl != PrevPwm)
      begin
              DeadTimeCounter <= DeadTime;
        if (PwmControl)               
          PwmLreg <= 0;         
        else
          PwmHreg <= 0;        
      end     
         else if (DeadTimeCounter != 0)   

        DeadTimeCounter <= DeadTimeCounter - 1;     
      else
      begin      
        if (PwmControl)              
          PwmHreg <= 1;         
        else
          PwmLreg <= 1;           
      end     
    end