Diff: targets/hal/TARGET_Atmel/TARGET_SAM21/drivers/system/clock/clock_samd21_r21/clock_feature.h

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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/hal/TARGET_Atmel/TARGET_SAM21/drivers/system/clock/clock_samd21_r21/clock_feature.h	Wed Jul 01 09:45:11 2015 +0100
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+/**
+ * \file
+ *
+ * \brief SAM Clock Driver
+ *
+ * Copyright (C) 2012-2014 Atmel Corporation. All rights reserved.
+ *
+ * \asf_license_start
+ *
+ * \page License
+ *
+ * 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. The name of Atmel may not be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * 4. This software may only be redistributed and used in connection with an
+ *    Atmel microcontroller product.
+ *
+ * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
+ * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL 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.
+ *
+ * \asf_license_stop
+ *
+ */
+/**
+* Support and FAQ: visit <a href="http://www.atmel.com/design-support/">Atmel Support</a>
+*/
+#ifndef SYSTEM_CLOCK_FEATURE_H_INCLUDED
+#define SYSTEM_CLOCK_FEATURE_H_INCLUDED
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \defgroup asfdoc_sam0_system_clock_group SAM System Clock Management Driver (SYSTEM CLOCK)
+ *
+ * This driver for Atmel庐 | SMART SAM devices provides an interface for the configuration
+ * and management of the device's clocking related functions. This includes
+ * the various clock sources, bus clocks, and generic clocks within the device,
+ * with functions to manage the enabling, disabling, source selection, and
+ * prescaling of clocks to various internal peripherals.
+ *
+ * The following peripherals are used by this module:
+ *
+ * - GCLK (Generic Clock Management)
+ * - PM (Power Management)
+ * - SYSCTRL (Clock Source Control)
+ *
+ * The following devices can use this module:
+ *  - Atmel | SMART SAM D20/D21
+ *  - Atmel | SMART SAM R21
+ *  - Atmel | SMART SAM D10/D11
+ *
+ * The outline of this documentation is as follows:
+ *  - \ref asfdoc_sam0_system_clock_prerequisites
+ *  - \ref asfdoc_sam0_system_clock_module_overview
+ *  - \ref asfdoc_sam0_system_clock_special_considerations
+ *  - \ref asfdoc_sam0_system_clock_extra_info
+ *  - \ref asfdoc_sam0_system_clock_examples
+ *  - \ref asfdoc_sam0_system_clock_api_overview
+ *
+ *
+ * \section asfdoc_sam0_system_clock_prerequisites Prerequisites
+ *
+ * There are no prerequisites for this module.
+ *
+ *
+ * \section asfdoc_sam0_system_clock_module_overview Module Overview
+ * The SAM devices contain a sophisticated clocking system, which is designed
+ * to give the maximum flexibility to the user application. This system allows
+ * a system designer to tune the performance and power consumption of the device
+ * in a dynamic manner, to achieve the best trade-off between the two for a
+ * particular application.
+ *
+ * This driver provides a set of functions for the configuration and management
+ * of the various clock related functionality within the device.
+ *
+ * \subsection asfdoc_sam0_system_clock_module_features Driver Feature Macro Definition
+ * <table>
+ *	<tr>
+ *		<th>Driver Feature Macro</th>
+ *		<th>Supported devices</th>
+ *	</tr>
+ *	<tr>
+ *		<td>FEATURE_SYSTEM_CLOCK_DPLL</td>
+ *		<td>SAMD21, SAMR21, SAMD10, SAMD11</td>
+ *	</tr>
+ * </table>
+ * \note The specific features are only available in the driver when the
+ * selected device supports those features.
+ *
+ * \subsection asfdoc_sam0_system_clock_module_overview_clock_sources Clock Sources
+ * The SAM devices have a number of master clock source modules, each of
+ * which being capable of producing a stabilized output frequency, which can then
+ * be fed into the various peripherals and modules within the device.
+ *
+ * Possible clock source modules include internal R/C oscillators, internal
+ * DFLL modules, as well as external crystal oscillators and/or clock inputs.
+ *
+ * \subsection asfdoc_sam0_system_clock_module_overview_cpu_clock CPU / Bus Clocks
+ * The CPU and AHB/APBx buses are clocked by the same physical clock source
+ * (referred in this module as the Main Clock), however the APBx buses may
+ * have additional prescaler division ratios set to give each peripheral bus a
+ * different clock speed.
+ *
+ * The general main clock tree for the CPU and associated buses is shown in
+ * \ref asfdoc_sam0_system_clock_module_clock_tree "the figure below".
+ *
+ * \anchor asfdoc_sam0_system_clock_module_clock_tree
+ * \dot
+ * digraph overview {
+ *   rankdir=LR;
+ *   clk_src [label="Clock Sources", shape=none, height=0];
+ *   node [label="CPU Bus" shape=ellipse] cpu_bus;
+ *   node [label="AHB Bus" shape=ellipse] ahb_bus;
+ *   node [label="APBA Bus" shape=ellipse] apb_a_bus;
+ *   node [label="APBB Bus" shape=ellipse] apb_b_bus;
+ *   node [label="APBC Bus" shape=ellipse] apb_c_bus;
+ *   node [label="Main Bus\nPrescaler" shape=square] main_prescaler;
+ *   node [label="APBA Bus\nPrescaler" shape=square] apb_a_prescaler;
+ *   node [label="APBB Bus\nPrescaler" shape=square] apb_b_prescaler;
+ *   node [label="APBC Bus\nPrescaler" shape=square] apb_c_prescaler;
+ *   node [label="", shape=polygon, sides=4, distortion=0.6, orientation=90, style=filled, fillcolor=black, height=0.9, width=0.2] main_clock_mux;
+ *
+ *   clk_src         -> main_clock_mux;
+ *   main_clock_mux  -> main_prescaler;
+ *   main_prescaler  -> cpu_bus;
+ *   main_prescaler  -> ahb_bus;
+ *   main_prescaler  -> apb_a_prescaler;
+ *   main_prescaler  -> apb_b_prescaler;
+ *   main_prescaler  -> apb_c_prescaler;
+ *   apb_a_prescaler -> apb_a_bus;
+ *   apb_b_prescaler -> apb_b_bus;
+ *   apb_c_prescaler -> apb_c_bus;
+ * }
+ * \enddot
+ *
+ * \subsection asfdoc_sam0_system_clock_module_overview_clock_masking Clock Masking
+ * To save power, the input clock to one or more peripherals on the AHB and APBx
+ * buses can be masked away - when masked, no clock is passed into the module.
+ * Disabling of clocks of unused modules will prevent all access to the masked
+ * module, but will reduce the overall device power consumption.
+ *
+ * \subsection asfdoc_sam0_system_clock_module_overview_gclk Generic Clocks
+ * Within the SAM devices there are a number of Generic Clocks; these are used to
+ * provide clocks to the various peripheral clock domains in the device in a
+ * standardized manner. One or more master source clocks can be selected as the
+ * input clock to a Generic Clock Generator, which can prescale down the input
+ * frequency to a slower rate for use in a peripheral.
+ *
+ * Additionally, a number of individually selectable Generic Clock Channels are
+ * provided, which multiplex and gate the various generator outputs for one or
+ * more peripherals within the device. This setup allows for a single common
+ * generator to feed one or more channels, which can then be enabled or disabled
+ * individually as required.
+ *
+ * \anchor asfdoc_sam0_system_clock_module_chain_overview
+ * \dot
+ * digraph overview {
+ *   rankdir=LR;
+ *   node [label="Clock\nSource a" shape=square] system_clock_source;
+ *   node [label="Generator 1" shape=square] clock_gen;
+ *   node [label="Channel x" shape=square] clock_chan0;
+ *   node [label="Channel y" shape=square] clock_chan1;
+ *   node [label="Peripheral x" shape=ellipse style=filled fillcolor=lightgray] peripheral0;
+ *   node [label="Peripheral y" shape=ellipse style=filled fillcolor=lightgray] peripheral1;
+ *
+ *   system_clock_source -> clock_gen;
+ *   clock_gen   -> clock_chan0;
+ *   clock_chan0 -> peripheral0;
+ *   clock_gen   -> clock_chan1;
+ *   clock_chan1 -> peripheral1;
+ * }
+ * \enddot
+ *
+ * \subsubsection asfdoc_sam0_system_clock_module_chain_example Clock Chain Example
+ * An example setup of a complete clock chain within the device is shown in
+ * \ref asfdoc_sam0_system_clock_module_chain_example_fig "the figure below".
+ *
+ * \anchor asfdoc_sam0_system_clock_module_chain_example_fig
+ * \dot
+ * digraph overview {
+ *   rankdir=LR;
+ *   node [label="External\nOscillator" shape=square] system_clock_source0;
+ *   node [label="Generator 0" shape=square] clock_gen0;
+ *   node [label="Channel x" shape=square] clock_chan0;
+ *   node [label="Core CPU" shape=ellipse  style=filled fillcolor=lightgray] peripheral0;
+ *
+ *   system_clock_source0 -> clock_gen0;
+ *   clock_gen0    -> clock_chan0;
+ *   clock_chan0   -> peripheral0;
+ *   node [label="8MHz R/C\nOscillator (OSC8M)" shape=square fillcolor=white] system_clock_source1;
+ *   node [label="Generator 1" shape=square] clock_gen1;
+ *   node [label="Channel y" shape=square] clock_chan1;
+ *   node [label="Channel z" shape=square] clock_chan2;
+ *   node [label="SERCOM\nModule" shape=ellipse  style=filled fillcolor=lightgray] peripheral1;
+ *   node [label="Timer\nModule" shape=ellipse  style=filled fillcolor=lightgray] peripheral2;
+ *
+ *   system_clock_source1 -> clock_gen1;
+ *   clock_gen1    -> clock_chan1;
+ *   clock_gen1    -> clock_chan2;
+ *   clock_chan1   -> peripheral1;
+ *   clock_chan2   -> peripheral2;
+ * }
+ * \enddot
+ *
+ * \subsubsection asfdoc_sam0_system_clock_module_overview_gclk_generators Generic Clock Generators
+ * Each Generic Clock generator within the device can source its input clock
+ * from one of the provided Source Clocks, and prescale the output for one or
+ * more Generic Clock Channels in a one-to-many relationship. The generators
+ * thus allow for several clocks to be generated of different frequencies,
+ * power usages, and accuracies, which can be turned on and off individually to
+ * disable the clocks to multiple peripherals as a group.
+ *
+ * \subsubsection asfdoc_sam0_system_clock_module_overview_gclk_channels Generic Clock Channels
+ * To connect a Generic Clock Generator to a peripheral within the
+ * device, a Generic Clock Channel is used. Each peripheral or
+ * peripheral group has an associated Generic Clock Channel, which serves as the
+ * clock input for the peripheral(s). To supply a clock to the peripheral
+ * module(s), the associated channel must be connected to a running Generic
+ * Clock Generator and the channel enabled.
+ *
+ * \section asfdoc_sam0_system_clock_special_considerations Special Considerations
+ *
+ * There are no special considerations for this module.
+ *
+ *
+ * \section asfdoc_sam0_system_clock_extra_info Extra Information
+ *
+ * For extra information, see \ref asfdoc_sam0_system_clock_extra. This includes:
+ *  - \ref asfdoc_sam0_system_clock_extra_acronyms
+ *  - \ref asfdoc_sam0_system_clock_extra_dependencies
+ *  - \ref asfdoc_sam0_system_clock_extra_errata
+ *  - \ref asfdoc_sam0_system_clock_extra_history
+ *
+ *
+ * \section asfdoc_sam0_system_clock_examples Examples
+ *
+ * For a list of examples related to this driver, see
+ * \ref asfdoc_sam0_system_clock_exqsg.
+ *
+ *
+ * \section asfdoc_sam0_system_clock_api_overview API Overview
+ * @{
+ */
+
+#include <compiler.h>
+
+#include <status_codes.h>
+/**
+ * \name Driver Feature Definition
+ * Define system clock features set according to different device family.
+ * @{
+ */
+#if (SAMD21) || (SAMR21) || (SAMD11) || (SAMD10) || defined(__DOXYGEN__)
+/** Digital Phase Locked Loop (DPLL) feature support. */
+#  define FEATURE_SYSTEM_CLOCK_DPLL
+#endif
+/*@}*/
+
+/**
+ * \brief Available start-up times for the XOSC32K.
+ *
+ * Available external 32KHz oscillator start-up times, as a number of external
+ * clock cycles.
+ */
+enum system_xosc32k_startup {
+    /** Wait zero clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC32K_STARTUP_0,
+    /** Wait 32 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC32K_STARTUP_32,
+    /** Wait 2048 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC32K_STARTUP_2048,
+    /** Wait 4096 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC32K_STARTUP_4096,
+    /** Wait 16384 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC32K_STARTUP_16384,
+    /** Wait 32768 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC32K_STARTUP_32768,
+    /** Wait 65536 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC32K_STARTUP_65536,
+    /** Wait 131072 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC32K_STARTUP_131072,
+};
+
+/**
+ * \brief Available start-up times for the XOSC.
+ *
+ * Available external oscillator start-up times, as a number of external clock
+ * cycles.
+ */
+enum system_xosc_startup {
+    /** Wait one clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_1,
+    /** Wait two clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_2,
+    /** Wait four clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_4,
+    /** Wait eight clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_8,
+    /** Wait 16 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_16,
+    /** Wait 32 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_32,
+    /** Wait 64 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_64,
+    /** Wait 128 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_128,
+    /** Wait 256 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_256,
+    /** Wait 512 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_512,
+    /** Wait 1024 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_1024,
+    /** Wait 2048 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_2048,
+    /** Wait 4096 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_4096,
+    /** Wait 8192 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_8192,
+    /** Wait 16384 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_16384,
+    /** Wait 32768 clock cycles until the clock source is considered stable. */
+    SYSTEM_XOSC_STARTUP_32768,
+};
+
+/**
+ * \brief Available start-up times for the OSC32K.
+ *
+ * Available internal 32KHz oscillator start-up times, as a number of internal
+ * OSC32K clock cycles.
+ */
+enum system_osc32k_startup {
+    /** Wait three clock cycles until the clock source is considered stable. */
+    SYSTEM_OSC32K_STARTUP_3,
+    /** Wait four clock cycles until the clock source is considered stable. */
+    SYSTEM_OSC32K_STARTUP_4,
+    /** Wait six clock cycles until the clock source is considered stable. */
+    SYSTEM_OSC32K_STARTUP_6,
+    /** Wait ten clock cycles until the clock source is considered stable. */
+    SYSTEM_OSC32K_STARTUP_10,
+    /** Wait 18 clock cycles until the clock source is considered stable. */
+    SYSTEM_OSC32K_STARTUP_18,
+    /** Wait 34 clock cycles until the clock source is considered stable */
+    SYSTEM_OSC32K_STARTUP_34,
+    /** Wait 66 clock cycles until the clock source is considered stable. */
+    SYSTEM_OSC32K_STARTUP_66,
+    /** Wait 130 clock cycles until the clock source is considered stable. */
+    SYSTEM_OSC32K_STARTUP_130,
+};
+
+/**
+ * \brief Division prescalers for the internal 8MHz system clock.
+ *
+ * Available prescalers for the internal 8MHz (nominal) system clock.
+ */
+enum system_osc8m_div {
+    /** Do not divide the 8MHz RC oscillator output. */
+    SYSTEM_OSC8M_DIV_1,
+    /** Divide the 8MHz RC oscillator output by two. */
+    SYSTEM_OSC8M_DIV_2,
+    /** Divide the 8MHz RC oscillator output by four. */
+    SYSTEM_OSC8M_DIV_4,
+    /** Divide the 8MHz RC oscillator output by eight. */
+    SYSTEM_OSC8M_DIV_8,
+};
+
+/**
+ * \brief Frequency range for the internal 8MHz RC oscillator.
+ *
+ * Internal 8MHz RC oscillator frequency range setting
+ */
+enum system_osc8m_frequency_range {
+    /** Frequency range 4MHz to 6MHz. */
+    SYSTEM_OSC8M_FREQUENCY_RANGE_4_TO_6,
+    /** Frequency range 6MHz to 8MHz. */
+    SYSTEM_OSC8M_FREQUENCY_RANGE_6_TO_8,
+    /** Frequency range 8MHz to 11MHz. */
+    SYSTEM_OSC8M_FREQUENCY_RANGE_8_TO_11,
+    /** Frequency range 11MHz to 15MHz. */
+    SYSTEM_OSC8M_FREQUENCY_RANGE_11_TO_15,
+};
+
+/**
+ * \brief Main CPU and APB/AHB bus clock source prescaler values.
+ *
+ * Available division ratios for the CPU and APB/AHB bus clocks.
+ */
+enum system_main_clock_div {
+    /** Divide Main clock by one. */
+    SYSTEM_MAIN_CLOCK_DIV_1,
+    /** Divide Main clock by two. */
+    SYSTEM_MAIN_CLOCK_DIV_2,
+    /** Divide Main clock by four. */
+    SYSTEM_MAIN_CLOCK_DIV_4,
+    /** Divide Main clock by eight. */
+    SYSTEM_MAIN_CLOCK_DIV_8,
+    /** Divide Main clock by 16. */
+    SYSTEM_MAIN_CLOCK_DIV_16,
+    /** Divide Main clock by 32. */
+    SYSTEM_MAIN_CLOCK_DIV_32,
+    /** Divide Main clock by 64. */
+    SYSTEM_MAIN_CLOCK_DIV_64,
+    /** Divide Main clock by 128. */
+    SYSTEM_MAIN_CLOCK_DIV_128,
+};
+
+/**
+ * \brief External clock source types.
+ *
+ * Available external clock source types.
+ */
+enum system_clock_external {
+    /** The external clock source is a crystal oscillator. */
+    SYSTEM_CLOCK_EXTERNAL_CRYSTAL,
+    /** The connected clock source is an external logic level clock signal. */
+    SYSTEM_CLOCK_EXTERNAL_CLOCK,
+};
+
+/**
+ * \brief Operating modes of the DFLL clock source.
+ *
+ * Available operating modes of the DFLL clock source module.
+ */
+enum system_clock_dfll_loop_mode {
+    /** The DFLL is operating in open loop mode with no feedback. */
+    SYSTEM_CLOCK_DFLL_LOOP_MODE_OPEN,
+    /** The DFLL is operating in closed loop mode with frequency feedback from
+     *  a low frequency reference clock.
+     */
+    SYSTEM_CLOCK_DFLL_LOOP_MODE_CLOSED = SYSCTRL_DFLLCTRL_MODE,
+
+#ifdef SYSCTRL_DFLLCTRL_USBCRM
+    /** The DFLL is operating in USB recovery mode with frequency feedback
+     *  from USB SOF.
+     */
+    SYSTEM_CLOCK_DFLL_LOOP_MODE_USB_RECOVERY = SYSCTRL_DFLLCTRL_USBCRM,
+#endif
+};
+
+/**
+ * \brief Locking behavior for the DFLL during device wake-up.
+ *
+ * DFLL lock behavior modes on device wake-up from sleep.
+ */
+enum system_clock_dfll_wakeup_lock {
+    /** Keep DFLL lock when the device wakes from sleep. */
+    SYSTEM_CLOCK_DFLL_WAKEUP_LOCK_KEEP,
+    /** Lose DFLL lock when the devices wakes from sleep. */
+    SYSTEM_CLOCK_DFLL_WAKEUP_LOCK_LOSE = SYSCTRL_DFLLCTRL_LLAW,
+};
+
+/**
+ * \brief Fine tracking behavior for the DFLL once a lock has been acquired.
+ *
+ * DFLL fine tracking behavior modes after a lock has been acquired.
+ */
+enum system_clock_dfll_stable_tracking {
+    /** Keep tracking after the DFLL has gotten a fine lock. */
+    SYSTEM_CLOCK_DFLL_STABLE_TRACKING_TRACK_AFTER_LOCK,
+    /** Stop tracking after the DFLL has gotten a fine lock. */
+    SYSTEM_CLOCK_DFLL_STABLE_TRACKING_FIX_AFTER_LOCK = SYSCTRL_DFLLCTRL_STABLE,
+};
+
+/**
+ * \brief Chill-cycle behavior of the DFLL module.
+ *
+ * DFLL chill-cycle behavior modes of the DFLL module. A chill cycle is a period
+ * of time when the DFLL output frequency is not measured by the unit, to allow
+ * the output to stabilize after a change in the input clock source.
+ */
+enum system_clock_dfll_chill_cycle {
+    /** Enable a chill cycle, where the DFLL output frequency is not measured. */
+    SYSTEM_CLOCK_DFLL_CHILL_CYCLE_ENABLE,
+    /** Disable a chill cycle, where the DFLL output frequency is not measured. */
+    SYSTEM_CLOCK_DFLL_CHILL_CYCLE_DISABLE = SYSCTRL_DFLLCTRL_CCDIS,
+};
+
+/**
+ * \brief QuickLock settings for the DFLL module.
+ *
+ * DFLL QuickLock settings for the DFLL module, to allow for a faster lock of
+ * the DFLL output frequency at the expense of accuracy.
+ */
+enum system_clock_dfll_quick_lock {
+    /** Enable the QuickLock feature for looser lock requirements on the DFLL. */
+    SYSTEM_CLOCK_DFLL_QUICK_LOCK_ENABLE,
+    /** Disable the QuickLock feature for strict lock requirements on the DFLL. */
+    SYSTEM_CLOCK_DFLL_QUICK_LOCK_DISABLE = SYSCTRL_DFLLCTRL_QLDIS,
+};
+
+/**
+ * \brief Available clock sources in the system.
+ *
+ * Clock sources available to the GCLK generators.
+ */
+enum system_clock_source {
+    /** Internal 8MHz RC oscillator. */
+    SYSTEM_CLOCK_SOURCE_OSC8M    = GCLK_SOURCE_OSC8M,
+    /** Internal 32KHz RC oscillator. */
+    SYSTEM_CLOCK_SOURCE_OSC32K   = GCLK_SOURCE_OSC32K,
+    /** External oscillator. */
+    SYSTEM_CLOCK_SOURCE_XOSC     = GCLK_SOURCE_XOSC ,
+    /** External 32KHz oscillator. */
+    SYSTEM_CLOCK_SOURCE_XOSC32K  = GCLK_SOURCE_XOSC32K,
+    /** Digital Frequency Locked Loop (DFLL). */
+    SYSTEM_CLOCK_SOURCE_DFLL     = GCLK_SOURCE_DFLL48M,
+    /** Internal Ultra Low Power 32KHz oscillator. */
+    SYSTEM_CLOCK_SOURCE_ULP32K   = GCLK_SOURCE_OSCULP32K,
+    /** Generator input pad */
+    SYSTEM_CLOCK_SOURCE_GCLKIN     = GCLK_SOURCE_GCLKIN,
+    /** Generic clock generator one output */
+    SYSTEM_CLOCK_SOURCE_GCLKGEN1   = GCLK_SOURCE_GCLKGEN1,
+#ifdef FEATURE_SYSTEM_CLOCK_DPLL
+    /** Digital Phase Locked Loop (DPLL).
+     * Check \c FEATURE_SYSTEM_CLOCK_DPLL for which device support it.
+     */
+    SYSTEM_CLOCK_SOURCE_DPLL     = GCLK_SOURCE_FDPLL,
+#endif
+};
+
+/**
+ * \brief List of APB peripheral buses.
+ *
+ * Available bus clock domains on the APB bus.
+ */
+enum system_clock_apb_bus {
+    /** Peripheral bus A on the APB bus. */
+    SYSTEM_CLOCK_APB_APBA,
+    /** Peripheral bus B on the APB bus. */
+    SYSTEM_CLOCK_APB_APBB,
+    /** Peripheral bus C on the APB bus. */
+    SYSTEM_CLOCK_APB_APBC,
+};
+
+/**
+ * \brief Configuration structure for XOSC.
+ *
+ * External oscillator clock configuration structure.
+ */
+struct system_clock_source_xosc_config {
+    /** External clock type. */
+    enum system_clock_external external_clock;
+    /** Crystal oscillator start-up time. */
+    enum system_xosc_startup startup_time;
+    /** Enable automatic amplitude gain control. */
+    bool auto_gain_control;
+    /** External clock/crystal frequency. */
+    uint32_t frequency;
+    /** Keep the XOSC enabled in standby sleep mode. */
+    bool run_in_standby;
+    /** Run On Demand. If this is set the XOSC won't run
+     * until requested by a peripheral. */
+    bool on_demand;
+};
+
+/**
+ * \brief Configuration structure for XOSC32K.
+ *
+ * External 32KHz oscillator clock configuration structure.
+ */
+struct system_clock_source_xosc32k_config {
+    /** External clock type. */
+    enum system_clock_external external_clock;
+    /** Crystal oscillator start-up time. */
+    enum system_xosc32k_startup startup_time;
+    /** Enable automatic amplitude control. */
+    bool auto_gain_control;
+    /** Enable 1KHz output. */
+    bool enable_1khz_output;
+    /** Enable 32KHz output. */
+    bool enable_32khz_output;
+    /** External clock/crystal frequency. */
+    uint32_t frequency;
+    /** Keep the XOSC32K enabled in standby sleep mode. */
+    bool run_in_standby;
+    /** Run On Demand. If this is set the XOSC32K won't run
+     * until requested by a peripheral. */
+    bool on_demand;
+    /** Lock configuration after it has been written,
+     *  a device reset will release the lock. */
+    bool write_once;
+};
+
+/**
+ * \brief Configuration structure for OSC8M.
+ *
+ * Internal 8MHz (nominal) oscillator configuration structure.
+ */
+struct system_clock_source_osc8m_config {
+    /* Internal 8MHz RC oscillator prescaler. */
+    enum system_osc8m_div prescaler;
+    /** Keep the OSC8M enabled in standby sleep mode. */
+    bool run_in_standby;
+    /** Run On Demand. If this is set the OSC8M won't run
+     * until requested by a peripheral. */
+    bool on_demand;
+};
+
+/**
+ * \brief Configuration structure for OSC32K.
+ *
+ * Internal 32KHz (nominal) oscillator configuration structure.
+ */
+struct system_clock_source_osc32k_config {
+    /** Startup time. */
+    enum system_osc32k_startup startup_time;
+    /** Enable 1KHz output. */
+    bool enable_1khz_output;
+    /** Enable 32KHz output. */
+    bool enable_32khz_output;
+    /** Keep the OSC32K enabled in standby sleep mode. */
+    bool run_in_standby;
+    /** Run On Demand. If this is set the OSC32K won't run
+     * until requested by a peripheral. */
+    bool on_demand;
+    /** Lock configuration after it has been written,
+     *  a device reset will release the lock. */
+    bool write_once;
+};
+
+/**
+ * \brief Configuration structure for DFLL.
+ *
+ * DFLL oscillator configuration structure.
+ */
+struct system_clock_source_dfll_config {
+    /** Loop mode. */
+    enum system_clock_dfll_loop_mode loop_mode;
+    /** Run On Demand. If this is set the DFLL won't run
+     * until requested by a peripheral. */
+    bool on_demand;
+    /** Enable Quick Lock. */
+    enum system_clock_dfll_quick_lock quick_lock;
+    /** Enable Chill Cycle. */
+    enum system_clock_dfll_chill_cycle chill_cycle;
+    /** DFLL lock state on wakeup. */
+    enum system_clock_dfll_wakeup_lock wakeup_lock;
+    /** DFLL tracking after fine lock. */
+    enum system_clock_dfll_stable_tracking stable_tracking;
+    /** Coarse calibration value (Open loop mode). */
+    uint8_t coarse_value;
+    /** Fine calibration value (Open loop mode). */
+    uint16_t fine_value;
+    /** Coarse adjustment maximum step size (Closed loop mode). */
+    uint8_t coarse_max_step;
+    /** Fine adjustment maximum step size (Closed loop mode). */
+    uint16_t fine_max_step;
+    /** DFLL multiply factor (Closed loop mode. */
+    uint16_t multiply_factor;
+};
+
+/**
+ * \name External Oscillator Management
+ * @{
+ */
+
+/**
+ * \brief Retrieve the default configuration for XOSC.
+ *
+ * Fills a configuration structure with the default configuration for an
+ * external oscillator module:
+ *   - External Crystal
+ *   - Start-up time of 16384 external clock cycles
+ *   - Automatic crystal gain control mode enabled
+ *   - Frequency of 12MHz
+ *   - Don't run in STANDBY sleep mode
+ *   - Run only when requested by peripheral (on demand)
+ *
+ * \param[out] config  Configuration structure to fill with default values
+ */
+static inline void system_clock_source_xosc_get_config_defaults(
+    struct system_clock_source_xosc_config *const config)
+{
+    Assert(config);
+
+    config->external_clock    = SYSTEM_CLOCK_EXTERNAL_CRYSTAL;
+    config->startup_time      = SYSTEM_XOSC_STARTUP_16384;
+    config->auto_gain_control = true;
+    config->frequency         = 12000000UL;
+    config->run_in_standby    = false;
+    config->on_demand         = true;
+}
+
+void system_clock_source_xosc_set_config(
+    struct system_clock_source_xosc_config *const config);
+
+/**
+ * @}
+ */
+
+
+/**
+ * \name External 32KHz Oscillator Management
+ * @{
+ */
+
+/**
+ * \brief Retrieve the default configuration for XOSC32K.
+ *
+ * Fills a configuration structure with the default configuration for an
+ * external 32KHz oscillator module:
+ *   - External Crystal
+ *   - Start-up time of 16384 external clock cycles
+ *   - Automatic crystal gain control mode disabled
+ *   - Frequency of 32.768KHz
+ *   - 1KHz clock output disabled
+ *   - 32KHz clock output enabled
+ *   - Don't run in STANDBY sleep mode
+ *   - Run only when requested by peripheral (on demand)
+ *   - Don't lock registers after configuration has been written
+ *
+ * \param[out] config  Configuration structure to fill with default values
+ */
+static inline void system_clock_source_xosc32k_get_config_defaults(
+    struct system_clock_source_xosc32k_config *const config)
+{
+    Assert(config);
+
+    config->external_clock      = SYSTEM_CLOCK_EXTERNAL_CRYSTAL;
+    config->startup_time        = SYSTEM_XOSC32K_STARTUP_16384;
+    config->auto_gain_control   = false;
+    config->frequency           = 32768UL;
+    config->enable_1khz_output  = false;
+    config->enable_32khz_output = true;
+    config->run_in_standby      = false;
+    config->on_demand           = true;
+    config->write_once          = false;
+}
+
+void system_clock_source_xosc32k_set_config(
+    struct system_clock_source_xosc32k_config *const config);
+/**
+ * @}
+ */
+
+
+/**
+ * \name Internal 32KHz Oscillator Management
+ * @{
+ */
+
+/**
+ * \brief Retrieve the default configuration for OSC32K.
+ *
+ * Fills a configuration structure with the default configuration for an
+ * internal 32KHz oscillator module:
+ *   - 1KHz clock output enabled
+ *   - 32KHz clock output enabled
+ *   - Don't run in STANDBY sleep mode
+ *   - Run only when requested by peripheral (on demand)
+ *   - Set startup time to 130 cycles
+ *   - Don't lock registers after configuration has been written
+ *
+ * \param[out] config  Configuration structure to fill with default values
+ */
+static inline void system_clock_source_osc32k_get_config_defaults(
+    struct system_clock_source_osc32k_config *const config)
+{
+    Assert(config);
+
+    config->enable_1khz_output  = true;
+    config->enable_32khz_output = true;
+    config->run_in_standby      = false;
+    config->on_demand           = true;
+    config->startup_time        = SYSTEM_OSC32K_STARTUP_130;
+    config->write_once          = false;
+}
+
+void system_clock_source_osc32k_set_config(
+    struct system_clock_source_osc32k_config *const config);
+
+/**
+ * @}
+ */
+
+
+/**
+ * \name Internal 8MHz Oscillator Management
+ * @{
+ */
+
+/**
+ * \brief Retrieve the default configuration for OSC8M.
+ *
+ * Fills a configuration structure with the default configuration for an
+ * internal 8MHz (nominal) oscillator module:
+ *   - Clock output frequency divided by a factor of eight
+ *   - Don't run in STANDBY sleep mode
+ *   - Run only when requested by peripheral (on demand)
+ *
+ * \param[out] config  Configuration structure to fill with default values
+ */
+static inline void system_clock_source_osc8m_get_config_defaults(
+    struct system_clock_source_osc8m_config *const config)
+{
+    Assert(config);
+
+    config->prescaler       = SYSTEM_OSC8M_DIV_8;
+    config->run_in_standby  = false;
+    config->on_demand       = true;
+}
+
+void system_clock_source_osc8m_set_config(
+    struct system_clock_source_osc8m_config *const config);
+
+/**
+ * @}
+ */
+
+
+/**
+ * \name Internal DFLL Management
+ * @{
+ */
+
+/**
+ * \brief Retrieve the default configuration for DFLL.
+ *
+ * Fills a configuration structure with the default configuration for a
+ * DFLL oscillator module:
+ *   - Open loop mode
+ *   - QuickLock mode enabled
+ *   - Chill cycle enabled
+ *   - Output frequency lock maintained during device wake-up
+ *   - Continuous tracking of the output frequency
+ *   - Default tracking values at the mid-points for both coarse and fine
+ *     tracking parameters
+ *   - Don't run in STANDBY sleep mode
+ *   - Run only when requested by peripheral (on demand)
+ *
+ * \param[out] config  Configuration structure to fill with default values
+ */
+static inline void system_clock_source_dfll_get_config_defaults(
+    struct system_clock_source_dfll_config *const config)
+{
+    Assert(config);
+
+    config->loop_mode       = SYSTEM_CLOCK_DFLL_LOOP_MODE_OPEN;
+    config->quick_lock      = SYSTEM_CLOCK_DFLL_QUICK_LOCK_ENABLE;
+    config->chill_cycle     = SYSTEM_CLOCK_DFLL_CHILL_CYCLE_ENABLE;
+    config->wakeup_lock     = SYSTEM_CLOCK_DFLL_WAKEUP_LOCK_KEEP;
+    config->stable_tracking = SYSTEM_CLOCK_DFLL_STABLE_TRACKING_TRACK_AFTER_LOCK;
+    config->on_demand       = true;
+
+    /* Open loop mode calibration value */
+    config->coarse_value    = 0x1f / 4; /* Midpoint */
+    config->fine_value      = 0xff / 4; /* Midpoint */
+
+    /* Closed loop mode */
+    config->coarse_max_step = 1;
+    config->fine_max_step   = 1;
+    config->multiply_factor = 6; /* Multiply 8MHz by 6 to get 48MHz */
+}
+
+void system_clock_source_dfll_set_config(
+    struct system_clock_source_dfll_config *const config);
+
+/**
+ * @}
+ */
+
+/**
+ * \name Clock Source Management
+ * @{
+ */
+enum status_code system_clock_source_write_calibration(
+    const enum system_clock_source system_clock_source,
+    const uint16_t calibration_value,
+    const uint8_t freq_range);
+
+enum status_code system_clock_source_enable(
+    const enum system_clock_source system_clock_source);
+
+enum status_code system_clock_source_disable(
+    const enum system_clock_source clk_source);
+
+bool system_clock_source_is_ready(
+    const enum system_clock_source clk_source);
+
+uint32_t system_clock_source_get_hz(
+    const enum system_clock_source clk_source);
+
+/**
+ * @}
+ */
+
+/**
+ * \name Main Clock Management
+ * @{
+ */
+
+/**
+ * \brief Set main CPU clock divider.
+ *
+ * Sets the clock divider used on the main clock to provide the CPU clock.
+ *
+ * \param[in] divider  CPU clock divider to set
+ */
+static inline void system_cpu_clock_set_divider(
+    const enum system_main_clock_div divider)
+{
+    Assert(((uint32_t)divider & PM_CPUSEL_CPUDIV_Msk) == divider);
+    PM->CPUSEL.reg = (uint32_t)divider;
+}
+
+/**
+ * \brief Retrieves the current frequency of the CPU core.
+ *
+ * Retrieves the operating frequency of the CPU core, obtained from the main
+ * generic clock and the set CPU bus divider.
+ *
+ * \return Current CPU frequency in Hz.
+ */
+static inline uint32_t system_cpu_clock_get_hz(void)
+{
+    return (system_gclk_gen_get_hz(GCLK_GENERATOR_0) >> PM->CPUSEL.reg);
+}
+
+/**
+ * \brief Set APBx clock divider.
+ *
+ * Set the clock divider used on the main clock to provide the clock for the
+ * given APBx bus.
+ *
+ * \param[in] divider  APBx bus divider to set
+ * \param[in] bus      APBx bus to set divider
+ *
+ * \returns Status of the clock division change operation.
+ *
+ * \retval STATUS_ERR_INVALID_ARG  Invalid bus ID was given
+ * \retval STATUS_OK               The APBx clock was set successfully
+ */
+static inline enum status_code system_apb_clock_set_divider(
+    const enum system_clock_apb_bus bus,
+    const enum system_main_clock_div divider)
+{
+    switch (bus) {
+        case SYSTEM_CLOCK_APB_APBA:
+                    PM->APBASEL.reg = (uint32_t)divider;
+                break;
+            case SYSTEM_CLOCK_APB_APBB:
+                PM->APBBSEL.reg = (uint32_t)divider;
+                break;
+            case SYSTEM_CLOCK_APB_APBC:
+                PM->APBCSEL.reg = (uint32_t)divider;
+                break;
+            default:
+                Assert(false);
+                return STATUS_ERR_INVALID_ARG;
+        }
+
+        return STATUS_OK;
+    }
+
+    /**
+     * \brief Retrieves the current frequency of a ABPx.
+     *
+     * Retrieves the operating frequency of an APBx bus, obtained from the main
+     * generic clock and the set APBx bus divider.
+     *
+     * \return Current APBx bus frequency in Hz.
+     */
+    static inline uint32_t system_apb_clock_get_hz(
+        const enum system_clock_apb_bus bus)
+{
+    uint16_t bus_divider = 0;
+
+    switch (bus) {
+        case SYSTEM_CLOCK_APB_APBA:
+            bus_divider = PM->APBASEL.reg;
+            break;
+        case SYSTEM_CLOCK_APB_APBB:
+            bus_divider = PM->APBBSEL.reg;
+            break;
+        case SYSTEM_CLOCK_APB_APBC:
+            bus_divider = PM->APBCSEL.reg;
+            break;
+        default:
+            Assert(false);
+            return 0;
+    }
+
+    return (system_gclk_gen_get_hz(GCLK_GENERATOR_0) >> bus_divider);
+}
+
+
+/**
+ * @}
+ */
+
+/**
+ * \name Bus Clock Masking
+ * @{
+ */
+
+/**
+ * \brief Set bits in the clock mask for the AHB bus.
+ *
+ * This function will set bits in the clock mask for the AHB bus.
+ * Any bits set to 1 will enable that clock, 0 bits in the mask
+ * will be ignored.
+ *
+ * \param[in] ahb_mask  AHB clock mask to enable
+ */
+static inline void system_ahb_clock_set_mask(
+    const uint32_t ahb_mask)
+{
+    PM->AHBMASK.reg |= ahb_mask;
+}
+
+/**
+ * \brief Clear bits in the clock mask for the AHB bus.
+ *
+ * This function will clear bits in the clock mask for the AHB bus.
+ * Any bits set to 1 will disable that clock, 0 bits in the mask
+ * will be ignored.
+ *
+ * \param[in] ahb_mask  AHB clock mask to disable
+ */
+static inline void system_ahb_clock_clear_mask(
+    const uint32_t ahb_mask)
+{
+    PM->AHBMASK.reg &= ~ahb_mask;
+}
+
+/**
+ * \brief Set bits in the clock mask for an APBx bus.
+ *
+ * This function will set bits in the clock mask for an APBx bus.
+ * Any bits set to 1 will enable the corresponding module clock, zero bits in
+ * the mask will be ignored.
+ *
+ * \param[in] mask  APBx clock mask, a \c SYSTEM_CLOCK_APB_APBx constant from
+ *                  the device header files
+ * \param[in] bus   Bus to set clock mask bits for, a mask of \c PM_APBxMASK_*
+ *                  constants from the device header files
+ *
+ * \returns Status indicating the result of the clock mask change operation.
+ *
+ * \retval STATUS_ERR_INVALID_ARG  Invalid bus given
+ * \retval STATUS_OK               The clock mask was set successfully
+ */
+static inline enum status_code system_apb_clock_set_mask(
+    const enum system_clock_apb_bus bus,
+    const uint32_t mask)
+{
+    switch (bus) {
+        case SYSTEM_CLOCK_APB_APBA:
+                    PM->APBAMASK.reg |= mask;
+                break;
+
+            case SYSTEM_CLOCK_APB_APBB:
+                PM->APBBMASK.reg |= mask;
+                break;
+
+            case SYSTEM_CLOCK_APB_APBC:
+                PM->APBCMASK.reg |= mask;
+                break;
+
+            default:
+                Assert(false);
+                return STATUS_ERR_INVALID_ARG;
+
+        }
+
+        return STATUS_OK;
+    }
+
+    /**
+     * \brief Clear bits in the clock mask for an APBx bus.
+     *
+     * This function will clear bits in the clock mask for an APBx bus.
+     * Any bits set to 1 will disable the corresponding module clock, zero bits in
+     * the mask will be ignored.
+     *
+     * \param[in] mask  APBx clock mask, a \c SYSTEM_CLOCK_APB_APBx constant from
+     *                  the device header files
+     * \param[in] bus   Bus to clear clock mask bits
+     *
+     * \returns Status indicating the result of the clock mask change operation.
+     *
+     * \retval STATUS_ERR_INVALID_ARG  Invalid bus ID was given
+     * \retval STATUS_OK               The clock mask was changed successfully
+     */
+    static inline enum status_code system_apb_clock_clear_mask(
+        const enum system_clock_apb_bus bus,
+        const uint32_t mask)
+{
+    switch (bus) {
+        case SYSTEM_CLOCK_APB_APBA:
+                    PM->APBAMASK.reg &= ~mask;
+                break;
+
+            case SYSTEM_CLOCK_APB_APBB:
+                PM->APBBMASK.reg &= ~mask;
+                break;
+
+            case SYSTEM_CLOCK_APB_APBC:
+                PM->APBCMASK.reg &= ~mask;
+                break;
+
+            default:
+                Assert(false);
+                return STATUS_ERR_INVALID_ARG;
+        }
+
+        return STATUS_OK;
+    }
+
+    /**
+     * @}
+     */
+
+#ifdef FEATURE_SYSTEM_CLOCK_DPLL
+    /**
+     * \brief Reference clock source of the DPLL module.
+     */
+    enum system_clock_source_dpll_reference_clock {
+    /** Select CLK_DPLL_REF0 as clock reference. */
+    SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_REF0,
+    /** Select CLK_DPLL_REF1 as clock reference. */
+    SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_REF1,
+    /** Select GCLK_DPLL as clock reference. */
+    SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_GCLK,
+};
+
+/**
+ * \brief Lock time-out value of the DPLL module.
+ */
+enum system_clock_source_dpll_lock_time {
+    /** Set no time-out as default. */
+    SYSTEM_CLOCK_SOURCE_DPLL_LOCK_TIME_DEFAULT,
+    /** Set time-out if no lock within 8ms. */
+    SYSTEM_CLOCK_SOURCE_DPLL_LOCK_TIME_8MS = 0x04,
+    /** Set time-out if no lock within 9ms. */
+    SYSTEM_CLOCK_SOURCE_DPLL_LOCK_TIME_9MS,
+    /** Set time-out if no lock within 10ms. */
+    SYSTEM_CLOCK_SOURCE_DPLL_LOCK_TIME_10MS,
+    /** Set time-out if no lock within 11ms. */
+    SYSTEM_CLOCK_SOURCE_DPLL_LOCK_TIME_11MS,
+};
+
+/**
+ * \brief Filter type of the DPLL module.
+ */
+enum system_clock_source_dpll_filter {
+    /** Default filter mode. */
+    SYSTEM_CLOCK_SOURCE_DPLL_FILTER_DEFAULT,
+    /** Low bandwidth filter. */
+    SYSTEM_CLOCK_SOURCE_DPLL_FILTER_LOW_BANDWIDTH_FILTER,
+    /** High bandwidth filter. */
+    SYSTEM_CLOCK_SOURCE_DPLL_FILTER_HIGH_BANDWIDTH_FILTER,
+    /** High damping filter. */
+    SYSTEM_CLOCK_SOURCE_DPLL_FILTER_HIGH_DAMPING_FILTER,
+};
+
+/**
+ * \brief Configuration structure for DPLL.
+ *
+ * DPLL oscillator configuration structure.
+ */
+struct system_clock_source_dpll_config {
+    /** Run On Demand. If this is set the DPLL won't run
+     * until requested by a peripheral. */
+    bool on_demand;
+    /** Keep the DPLL enabled in standby sleep mode. */
+    bool run_in_standby;
+    /** Bypass lock signal. */
+    bool lock_bypass;
+    /** Wake up fast. If this is set DPLL output clock is enabled after
+     * the startup time. */
+    bool wake_up_fast;
+    /** Enable low power mode.  */
+    bool low_power_enable;
+
+    /** Output frequency of the clock. */
+    uint32_t output_frequency;
+    /** Reference frequency of the clock. */
+    uint32_t reference_frequency;
+    /** Devider of reference clock. */
+    uint16_t reference_divider;
+
+    /** Filter type of the DPLL module. */
+    enum system_clock_source_dpll_filter          filter;
+    /** Lock time-out value of the DPLL module. */
+    enum system_clock_source_dpll_lock_time       lock_time;
+    /** Reference clock source of the DPLL module. */
+    enum system_clock_source_dpll_reference_clock reference_clock;
+};
+
+/**
+ * \name Internal DPLL Management
+ * @{
+ */
+
+/**
+ * \brief Retrieve the default configuration for DPLL.
+ *
+ * Fills a configuration structure with the default configuration for a
+ * DPLL oscillator module:
+ *   - Run only when requested by peripheral (on demand)
+ *   - Don't run in STANDBY sleep mode
+ *   - Lock bypass disabled
+ *   - Fast wake up disabled
+ *   - Low power mode disabled
+ *   - Output frequency is 48MHz
+ *   - Reference clock frequency is 32768Hz
+ *   - Not divide reference clock
+ *   - Select REF0 as reference clock
+ *   - Set lock time to default mode
+ *   - Use default filter
+ *
+ * \param[out] config  Configuration structure to fill with default values
+ */
+static inline void system_clock_source_dpll_get_config_defaults(
+    struct system_clock_source_dpll_config *const config)
+{
+    config->on_demand           = true;
+    config->run_in_standby      = false;
+    config->lock_bypass         = false;
+    config->wake_up_fast        = false;
+    config->low_power_enable    = false;
+
+    config->output_frequency    = 48000000;
+    config->reference_frequency = 32768;
+    config->reference_divider   = 1;
+    config->reference_clock     = SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_REF0;
+
+    config->lock_time           = SYSTEM_CLOCK_SOURCE_DPLL_LOCK_TIME_DEFAULT;
+    config->filter              = SYSTEM_CLOCK_SOURCE_DPLL_FILTER_DEFAULT;
+};
+
+void system_clock_source_dpll_set_config(
+    struct system_clock_source_dpll_config *const config);
+
+/* @} */
+#endif
+
+/**
+ * \name System Clock Initialization
+ * @{
+ */
+
+void system_clock_init(void);
+
+/**
+ * @}
+ */
+
+/**
+ * \name System Flash Wait States
+ * @{
+ */
+
+/**
+ * \brief Set flash controller wait states.
+ *
+ * Will set the number of wait states that are used by the onboard
+ * flash memory. The number of wait states depend on both device
+ * supply voltage and CPU speed. The required number of wait states
+ * can be found in the electrical characteristics of the device.
+ *
+ * \param[in] wait_states Number of wait states to use for internal flash
+ */
+static inline void system_flash_set_waitstates(uint8_t wait_states)
+{
+    Assert(NVMCTRL_CTRLB_RWS((uint32_t)wait_states) ==
+           ((uint32_t)wait_states << NVMCTRL_CTRLB_RWS_Pos));
+
+    NVMCTRL->CTRLB.bit.RWS = wait_states;
+}
+/**
+ * @}
+ */
+
+/**
+ * @}
+ */
+
+/**
+ * \page asfdoc_sam0_system_clock_extra Extra Information for SYSTEM CLOCK Driver
+ *
+ * \section asfdoc_sam0_system_clock_extra_acronyms Acronyms
+ * Below is a table listing the acronyms used in this module, along with their
+ * intended meanings.
+ *
+ * <table>
+ *	<tr>
+ *		<th>Acronym</th>
+ *		<th>Description</th>
+ *	</tr>
+ *	<tr>
+ *		<td>DFLL</td>
+ *		<td>Digital Frequency Locked Loop</td>
+ *	</tr>
+ *	<tr>
+ *		<td>MUX</td>
+ *		<td>Multiplexer</td>
+ *	</tr>
+ *	<tr>
+ *		<td>OSC32K</td>
+ *		<td>Internal 32KHz Oscillator</td>
+ *	</tr>
+ *	<tr>
+ *		<td>OSC8M</td>
+ *		<td>Internal 8MHz Oscillator</td>
+ *	</tr>
+ *	<tr>
+ *		<td>PLL</td>
+ *		<td>Phase Locked Loop</td>
+ *	</tr>
+ *	<tr>
+ *		<td>OSC</td>
+ *		<td>Oscillator</td>
+ *	</tr>
+ *	<tr>
+ *		<td>XOSC</td>
+ *		<td>External Oscillator</td>
+ *	</tr>
+ *	<tr>
+ *		<td>XOSC32K</td>
+ *		<td>External 32KHz Oscillator</td>
+ *	</tr>
+ *	<tr>
+ *		<td>AHB</td>
+ *		<td>Advanced High-performance Bus</td>
+ *	</tr>
+ *	<tr>
+ *		<td>APB</td>
+ *		<td>Advanced Peripheral Bus</td>
+ *	</tr>
+ *	<tr>
+ *		<td>DPLL</td>
+ *		<td>Digital Phase Locked Loop</td>
+ *	</tr>
+ * </table>
+ *
+ *
+ * \section asfdoc_sam0_system_clock_extra_dependencies Dependencies
+ * This driver has the following dependencies:
+ *
+ *  - None
+ *
+ *
+ * \section asfdoc_sam0_system_clock_extra_errata Errata
+ *
+ *	- This driver implements workaround for errata 10558
+ *
+ *	  "Several reset values of SYSCTRL.INTFLAG are wrong (BOD and DFLL)"
+ *	  When system_init is called it will reset these interrupts flags before they are used.
+
+ *	- This driver implements experimental workaround for errata 9905
+ *
+ *	  "The DFLL clock must be requested before being configured otherwise a
+ *	  write access to a DFLL register can freeze the device."
+ *	  This driver will enable and configure the DFLL before the ONDEMAND bit is set.
+ *
+ *
+ * \section asfdoc_sam0_system_clock_extra_history Module History
+ * An overview of the module history is presented in the table below, with
+ * details on the enhancements and fixes made to the module since its first
+ * release. The current version of this corresponds to the newest version in
+ * the table.
+ *
+ * <table>
+ *	<tr>
+ *		<th>Changelog</th>
+ *	</tr>
+ *	<tr>
+ *		<td>
+ *			\li Corrected OSC32K startup time definitions
+ *			\li Support locking of OSC32K and XOSC32K config register (default: false)
+ *			\li Added DPLL support, functions added:
+ *			    \c system_clock_source_dpll_get_config_defaults() and
+ *		        \c system_clock_source_dpll_set_config()
+ *			\li Moved gclk channel locking feature out of the config struct
+ *			    functions added:
+ *			    \c system_gclk_chan_lock(),
+ *			    \c system_gclk_chan_is_locked()
+ *			    \c system_gclk_chan_is_enabled() and
+ *			    \c system_gclk_gen_is_enabled()
+ *		</td>
+ *	</tr>
+ *  <tr>
+ *		<td>Fixed \c system_gclk_chan_disable() deadlocking if a channel is enabled
+ *		    and configured to a failed/not running clock generator</td>
+ *  </tr>
+ *	<tr>
+ *		<td>
+ *			\li Changed default value for CONF_CLOCK_DFLL_ON_DEMAND from \c true to \c false
+ *			\li Fixed system_flash_set_waitstates() failing with an assertion
+ *			    if an odd number of wait states provided
+ *		</td>
+ *	</tr>
+ *	<tr>
+ *		<td>
+ *			\li Updated dfll configuration function to implement workaround for
+ *			    errata 9905 in the DFLL module
+ *			\li Updated \c system_clock_init() to reset interrupt flags before
+ *			    they are used, errata 10558
+ *			\li Fixed \c system_clock_source_get_hz() to return correcy DFLL
+ *			    frequency number
+ *		</td>
+ *	</tr>
+ *	<tr>
+ *		<td>\li Fixed \c system_clock_source_is_ready not returning the correct
+ *              state for \c SYSTEM_CLOCK_SOURCE_OSC8M
+ *          \li Renamed the various \c system_clock_source_*_get_default_config()
+ *              functions to \c system_clock_source_*_get_config_defaults() to
+ *              match the remainder of ASF
+ *          \li Added OSC8M calibration constant loading from the device signature
+ *              row when the oscillator is initialized
+ *          \li Updated default configuration of the XOSC32 to disable Automatic
+ *              Gain Control due to silicon errata
+ *      </td>
+ *	</tr>
+ *	<tr>
+ *		<td>Initial Release</td>
+ *	</tr>
+ * </table>
+ */
+
+/**
+ * \page asfdoc_sam0_system_clock_exqsg Examples for System Clock Driver
+ *
+ * This is a list of the available Quick Start guides (QSGs) and example
+ * applications for \ref asfdoc_sam0_system_clock_group. QSGs are simple
+ * examples with step-by-step instructions to configure and use this driver in
+ * a selection of use cases. Note that QSGs can be compiled as a standalone
+ * application or be added to the user application.
+ *
+ *  - \subpage asfdoc_sam0_system_clock_basic_use_case
+ *  - \subpage asfdoc_sam0_system_gclk_basic_use_case
+ *
+ * \page asfdoc_sam0_system_clock_document_revision_history Document Revision History
+ *
+ * <table>
+ *	<tr>
+ *		<th>Doc. Rev.</td>
+ *		<th>Date</td>
+ *		<th>Comments</td>
+ *	</tr>
+ *	<tr>
+ *		<td>D</td>
+ *		<td>12/2014</td>
+ *		<td>Added support for SAMR21 and SAMD10/D11.</td>
+ *	</tr>
+ *	<tr>
+ *		<td>C</td>
+ *		<td>01/2014</td>
+ *		<td>Added support for SAMD21.</td>
+ *	</tr>
+ *	<tr>
+ *		<td>B</td>
+ *		<td>06/2013</td>
+ *		<td>Corrected documentation typos. Fixed missing steps in the Basic
+ *          Use Case Quick Start Guide.</td>
+ *	</tr>
+ *	<tr>
+ *		<td>A</td>
+ *		<td>06/2013</td>
+ *		<td>Initial release</td>
+ *	</tr>
+ * </table>
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SYSTEM_CLOCK_FEATURE_H_INCLUDED */