dft_clock_system                                   Defines a clock system,
                                                   either single-phase or
                                                   two-phase.
 [ tree ]                                            Applies the constraint to
                                                     all levels of hierarchy
                                                     below the object(s)
                                                     specified.
 [ -scope ]                 scope                    design unit/ current scope
 { -clock input_port        [ -edge edge ]           rise, fall /rise
   | -master input_port     [ -masterlevel level ]   high, low /high
     -slave input_port      [ -slavelevel level ] }  high, low /high
