code: def REV16(self, params):
          
          Ra, Rb = self.get_two_parameters(self.TWO_PARAMETER_COMMA_SEPARATED, params)
  
          self.check_arguments(low_registers=(Ra, Rb))
  
          def REV16_func():
              self.register[Ra] = ((self.register[Rb] & 0xFF00FF00) >> 8) | \
                                  ((self.register[Rb] & 0x00FF00FF) << 8)
  
          return REV16_func
docs: REV16 Ra, Rb
  
          Reverse the byte order of the half words in register Rb and store the result in Ra