CC2640 的示例工程pinShutdown中debounce period的意义是什么

请问：
1.CC2640 的示例工程pinShutdown中debounce period的意义是什么？
2.可不可以直接在btn回调函数中直接发shutdown信号量shutdownSem？

/*!*****************************************************************************
 *  @brief      Button clock callback
 *
 *  Called when the debounce periode is over. Stopping the clock, toggling
 *  the device mode based on activeButtonPinId:
 *
 *              KEY_DOWN will put the device in shutdown mode.
 *
 *  Reenabling the interrupts and resetting the activeButtonPinId.
 *
 *  @param      arg  argument (PIN_Handle) connected to the callback
 *
 ******************************************************************************/
static void buttonClockCb(UArg arg) {
    PIN_Handle buttonHandle = (PIN_State *) arg;

    /* Stop the button clock */
    Clock_stop(hButtonClock);

    /* Check that there is active button for debounce logic*/
    if (activeButtonPinId != PIN_TERMINATE) {
        /* Debounce logic, only toggle if the button is still pushed (low) */
        if (!PIN_getInputValue(activeButtonPinId)) {
            /* Toggle LED based on the button pressed */
            switch (activeButtonPinId) {
            case Board_BUTTON1:
                Semaphore_post(Semaphore_handle(&shutdownSem));
                break;
            default:
                /* Do nothing */
                break;
            }
        }
    }

    /* Re-enable interrupts to detect button release. */
    PIN_setConfig(buttonHandle, PIN_BM_IRQ, activeButtonPinId | PIN_IRQ_NEGEDGE);

    /* Set activeButtonPinId to none... */
    activeButtonPinId = PIN_TERMINATE;
}

/*!*****************************************************************************
 *  @brief      Button callback
 *
 *  Initiates the debounce period by disabling interrupts, setting a timeout
 *  for the button clock callback and starting the button clock.
 *  Sets the activeButtonPinId.
 *
 *  @param      handle PIN_Handle connected to the callback
 *
 *  @param      pinId  PIN_Id of the DIO triggering the callback
 *
 *  @return     none
 ******************************************************************************/
static void buttonCb(PIN_Handle handle, PIN_Id pinId) {

    // 可否在这里直接根据pinId(=1,发送信号量shutdownSem)


    /* Set current pinId to active */
    activeButtonPinId = pinId;

    /* Disable interrupts during debounce */
    PIN_setConfig(handle, PIN_BM_IRQ, activeButtonPinId | PIN_IRQ_DIS);

    /* Set timeout 50 ms from now and re-start clock */
    Clock_setTimeout(hButtonClock, (50 * (1000 / Clock_tickPeriod)));
    Clock_start(hButtonClock);
}