FLL的问题

  __bis_SR_register(SCG0);                  // Disable the FLL control loop  

 UCSCTL0 = 0x0000;   // Set lowest possible DCOx, MODx  

 UCSCTL1 = DCORSEL_5;                      // Select DCO range 16MHz operation  

UCSCTL2 = FLLD_1 + 249;                   // Set DCO Multiplier for 8MHz   

                                          // (N + 1) * FLLRef = Fdco      // (249 + 1) * 32768 = 8MHz              // Set FLL Div = fDCOCLK/2

  __bic_SR_register(SCG0);                  // Enable the FLL control loop

请问一下这里的UCSCTL1 = DCORSEL_5;   怎么得到DCO最大为16MHz，求解。谢谢！