nrf51-sdk/source/nordic_sdk/components/toolchain/system_nrf51.c

/*
 * Copyright (c) Nordic Semiconductor ASA
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright notice, this
 *   list of conditions and the following disclaimer in the documentation and/or
 *   other materials provided with the distribution.
 *
 *   3. Neither the name of Nordic Semiconductor ASA nor the names of other
 *   contributors to this software may be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

/* NOTE: Template files (including this one) are application specific and therefore expected to 
   be copied into the application project folder prior to its use! */

#include <stdint.h>
#include <stdbool.h>
#include "nrf.h"
#include "system_nrf51.h"

/*lint ++flb "Enter library region" */


#define __SYSTEM_CLOCK      (16000000UL)     /*!< nRF51 devices use a fixed System Clock Frequency of 16MHz */

static bool is_manual_peripheral_setup_needed(void);
static bool is_disabled_in_debug_needed(void);


#if defined ( __CC_ARM )
    uint32_t SystemCoreClock __attribute__((used)) = __SYSTEM_CLOCK;  
#elif defined ( __ICCARM__ )
    __root uint32_t SystemCoreClock = __SYSTEM_CLOCK;
#elif defined   ( __GNUC__ )
    uint32_t SystemCoreClock __attribute__((used)) = __SYSTEM_CLOCK;
#endif

#ifndef YOTTA_CFG_HARDWARE_CLOCKS_NRF_LFCLK_SRC
#   define YOTTA_CFG_HARDWARE_CLOCKS_NRF_LFCLK_SRC 1UL /* The default is to wait for LFLCK to start */
#endif

void SystemCoreClockUpdate(void)
{
    SystemCoreClock = __SYSTEM_CLOCK;
}

void SystemInit(void)
{
    /* If desired, switch off the unused RAM to lower consumption by the use of RAMON register.
       It can also be done in the application main() function. */

    /* Prepare the peripherals for use as indicated by the PAN 26 "System: Manual setup is required
       to enable the use of peripherals" found at Product Anomaly document for your device found at
       https://www.nordicsemi.com/. The side effect of executing these instructions in the devices 
       that do not need it is that the new peripherals in the second generation devices (LPCOMP for
       example) will not be available. */
    if (is_manual_peripheral_setup_needed())
    {
        *(uint32_t volatile *)0x40000504 = 0xC007FFDF;
        *(uint32_t volatile *)0x40006C18 = 0x00008000;
    }
    
    /* Disable PROTENSET registers under debug, as indicated by PAN 59 "MPU: Reset value of DISABLEINDEBUG
       register is incorrect" found at Product Anomaly document four your device found at 
       https://www.nordicsemi.com/. There is no side effect of using these instruction if not needed. */
    if (is_disabled_in_debug_needed())
    {
        NRF_MPU->DISABLEINDEBUG = MPU_DISABLEINDEBUG_DISABLEINDEBUG_Disabled << MPU_DISABLEINDEBUG_DISABLEINDEBUG_Pos;
    }

    // Start the external 32khz crystal oscillator.
    NRF_CLOCK->LFCLKSRC             = (YOTTA_CFG_HARDWARE_CLOCKS_NRF_LFCLK_SRC << CLOCK_LFCLKSRC_SRC_Pos);
    NRF_CLOCK->EVENTS_LFCLKSTARTED  = 0;
    NRF_CLOCK->TASKS_LFCLKSTART     = 1;

    // Wait for the external oscillator to start up.
    while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0) {
        // Do nothing.
    }
}


static bool is_manual_peripheral_setup_needed(void) 
{
    if ((((*(uint32_t *)0xF0000FE0) & 0x000000FF) == 0x1) && (((*(uint32_t *)0xF0000FE4) & 0x0000000F) == 0x0))
    {
        if ((((*(uint32_t *)0xF0000FE8) & 0x000000F0) == 0x00) && (((*(uint32_t *)0xF0000FEC) & 0x000000F0) == 0x0))
        {
            return true;
        }
        if ((((*(uint32_t *)0xF0000FE8) & 0x000000F0) == 0x10) && (((*(uint32_t *)0xF0000FEC) & 0x000000F0) == 0x0))
        {
            return true;
        }
        if ((((*(uint32_t *)0xF0000FE8) & 0x000000F0) == 0x30) && (((*(uint32_t *)0xF0000FEC) & 0x000000F0) == 0x0))
        {
            return true;
        }
    }
    
    return false;
}

static bool is_disabled_in_debug_needed(void) 
{
    if ((((*(uint32_t *)0xF0000FE0) & 0x000000FF) == 0x1) && (((*(uint32_t *)0xF0000FE4) & 0x0000000F) == 0x0))
    {
        if ((((*(uint32_t *)0xF0000FE8) & 0x000000F0) == 0x40) && (((*(uint32_t *)0xF0000FEC) & 0x000000F0) == 0x0))
        {
            return true;
        }
    }
    
    return false;
}

/*lint --flb "Leave library region" */