CC2640进入shutdown模式后，无法唤醒。代码如下

/* Wake-up Button pin table */
PIN_Config KeyTableWakeUp[] = {
    GUA_KEY_IO  | PIN_GPIO_OUTPUT_DIS  | PIN_INPUT_EN  |  PIN_PULLDOWN | PINCC26XX_WAKEUP_POSEDGE,
    PIN_TERMINATE                                 /* Terminate list */
};


      hKeyPins = PIN_open(&keyPins, KeyTableWakeUp); 
      PIN_setConfig(hKeyPins, PINCC26XX_BM_WAKEUP, GUA_KEY_IO | PINCC26XX_WAKEUP_POSEDGE);  
      /* Go to shutdown */
      Power_shutdown(NULL);
      /* Should never get here, since shutdown will reset. */
      while(1);

这样进入shutdown模式正确吗？为什么不能唤醒？