CC2538: CC2538 Watchdog won't stop under PM2

/******************************************************************************
*  Filename:       watchdog_simple.c
*  Revised:        $Date: 2013-04-10 10:58:59 +0200 (Wed, 10 Apr 2013) $
*  Revision:       $Revision: 9697 $
*
*  Description:    Example demonstrating how to configure the watchdog timer.
*
*  Copyright (C) 2013 Texas Instruments Incorporated - http://www.ti.com/
*
*
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*  modification, are permitted provided that the following conditions
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*
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******************************************************************************/

#include <stdbool.h>
#include <stdint.h>
#include "hw_memmap.h"
#include "gpio.h"
#include "hw_ioc.h"
#include "ioc.h"
#include "interrupt.h"
#include "sys_ctrl.h"
#include "systick.h"
#include "uartstdio.h"
#include "watchdog.h"

#include "hw_ints.h"
#include "sleepmode.h"
#include "uart.h"

//
//*****************************************************************************
//
//! \addtogroup watchdog_examples_list
//! <h1>Watch dog (watchdog_simple)</h1>
//!
//! This example shows how to configure and clear the watchdog timer.
//!
//! This example uses the following peripherals and I/O signals.  You must
//! review these and change as needed for your own board:
//! - NONE
//!
//! This example uses the following interrupt handlers.  To use this example
//! in your own application you can add these interrupt handlers to your
//! vector table.
//! - None
//!
//*****************************************************************************
#define EXAMPLE_PIN_LED_1            GPIO_PIN_0   //PC0
#define EXAMPLE_PIN_LED_2            GPIO_PIN_1   //PC1
#define EXAMPLE_GPIO_LED_BASE        GPIO_C_BASE


//*****************************************************************************
//
// Sleep mode timer ISR
//
//*****************************************************************************
void SleepModeIntHandler(void)
{
    GPIOPinWrite(EXAMPLE_GPIO_LED_BASE, 
                 EXAMPLE_PIN_LED_1,
                 0);
                 
    return;
}

//*****************************************************************************
//
//
//*****************************************************************************
int main(void)
{
    uint32_t ui32Val;
    //
    // Set the clocking to run directly from the external crystal/oscillator.
    // (no ext 32k osc, no internal osc)
    //
    //SysCtrlClockSet(false, false, SYS_CTRL_SYSDIV_32MHZ);
    SysCtrlClockSet(false, false, SYS_CTRL_SYSDIV_16MHZ);

    //
    // Set IO clock to the same as system clock
    //
    //SysCtrlIOClockSet(SYS_CTRL_SYSDIV_32MHZ);
    SysCtrlIOClockSet(SYS_CTRL_SYSDIV_16MHZ);
    
    GPIOPinTypeGPIOOutput(EXAMPLE_GPIO_LED_BASE,
                          (EXAMPLE_PIN_LED_1 | EXAMPLE_PIN_LED_2));
    
    GPIOPinWrite(EXAMPLE_GPIO_LED_BASE, 
                 EXAMPLE_PIN_LED_1,
                 1);
    GPIOPinWrite(EXAMPLE_GPIO_LED_BASE, 
                 EXAMPLE_PIN_LED_2,
                 1);
    
    //
    // Let system enter powermode 2 when going to deep sleep
    //
    SysCtrlPowerModeSet(SYS_CTRL_PM_2);

    //
    // Enable the Sleep Timer wakeup
    //
    GPIOIntWakeupEnable(GPIO_IWE_SM_TIMER); 

    //
    // Enable sleep mode interrupt
    //
    IntEnable(INT_SMTIM);
    
    //
    // Set timer to 10000
    //
    ui32Val = SleepModeTimerCountGet();
    SleepModeTimerCompareSet(ui32Val + 10000);
    GPIOPinWrite(EXAMPLE_GPIO_LED_BASE, 
             EXAMPLE_PIN_LED_1,
             1);

    //
    // Enable watchdog
    //
    //WatchdogEnable(WATCHDOG_INTERVAL_32768);  
    WatchdogEnable(WATCHDOG_INTERVAL_8192);
    
    while(1)
    {
        //
        // Go to sleep
        //
        SysCtrlDeepSleep();
    }
    
}