210 lines
8.4 KiB
C
210 lines
8.4 KiB
C
/*
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Copyright (c) 2015 Arduino LLC. All right reserved.
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Copyright (c) 2015 Atmel Corporation/Thibaut VIARD. All right reserved.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <sam.h>
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#include "board_definitions.h"
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/**
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* \brief system_init() configures the needed clocks and according Flash Read Wait States.
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* At reset:
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* - OSC8M clock source is enabled with a divider by 8 (1MHz).
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* - Generic Clock Generator 0 (GCLKMAIN) is using OSC8M as source.
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* We need to:
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* 1) Enable XOSC32K clock (External on-board 32.768Hz oscillator), will be used as DFLL48M reference.
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* 2) Put XOSC32K as source of Generic Clock Generator 1
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* 3) Put Generic Clock Generator 1 as source for Generic Clock Multiplexer 0 (DFLL48M reference)
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* 4) Enable DFLL48M clock
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* 5) Switch Generic Clock Generator 0 to DFLL48M. CPU will run at 48MHz.
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* 6) Modify PRESCaler value of OSCM to have 8MHz
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* 7) Put OSC8M as source for Generic Clock Generator 3
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*/
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// Constants for Clock generators
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#define GENERIC_CLOCK_GENERATOR_MAIN (0u)
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#define GENERIC_CLOCK_GENERATOR_XOSC32K (1u)
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#define GENERIC_CLOCK_GENERATOR_OSCULP32K (2u) /* Initialized at reset for WDT */
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#define GENERIC_CLOCK_GENERATOR_OSC8M (3u)
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// Constants for Clock multiplexers
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#define GENERIC_CLOCK_MULTIPLEXER_DFLL48M (0u)
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void board_init(void)
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{
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/* Set 1 Flash Wait State for 48MHz, cf tables 20.9 and 35.27 in SAMD21 Datasheet */
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NVMCTRL->CTRLB.bit.RWS = NVMCTRL_CTRLB_RWS_HALF_Val;
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/* Turn on the digital interface clock */
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PM->APBAMASK.reg |= PM_APBAMASK_GCLK;
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/* ----------------------------------------------------------------------------------------------
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* 1) Enable XOSC32K clock (External on-board 32.768Hz oscillator)
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*/
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SYSCTRL->XOSC32K.reg = SYSCTRL_XOSC32K_STARTUP( 0x6u ) | /* cf table 15.10 of product datasheet in chapter 15.8.6 */
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SYSCTRL_XOSC32K_XTALEN | SYSCTRL_XOSC32K_EN32K;
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SYSCTRL->XOSC32K.bit.ENABLE = 1; /* separate call, as described in chapter 15.6.3 */
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while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_XOSC32KRDY) == 0 )
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{
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/* Wait for oscillator stabilization */
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}
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/* Software reset the module to ensure it is re-initialized correctly */
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/* Note: Due to synchronization, there is a delay from writing CTRL.SWRST until the reset is complete.
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* CTRL.SWRST and STATUS.SYNCBUSY will both be cleared when the reset is complete, as described in chapter 13.8.1
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*/
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GCLK->CTRL.reg = GCLK_CTRL_SWRST;
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while ( (GCLK->CTRL.reg & GCLK_CTRL_SWRST) && (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY) )
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{
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/* Wait for reset to complete */
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}
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/* ----------------------------------------------------------------------------------------------
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* 2) Put XOSC32K as source of Generic Clock Generator 1
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*/
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GCLK->GENDIV.reg = GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_XOSC32K ); // Generic Clock Generator 1
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while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
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{
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/* Wait for synchronization */
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}
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/* Write Generic Clock Generator 1 configuration */
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GCLK->GENCTRL.reg = GCLK_GENCTRL_ID( GENERIC_CLOCK_GENERATOR_XOSC32K ) | // Generic Clock Generator 1
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GCLK_GENCTRL_SRC_XOSC32K | // Selected source is External 32KHz Oscillator
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// GCLK_GENCTRL_OE | // Output clock to a pin for tests
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GCLK_GENCTRL_GENEN;
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while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
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{
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/* Wait for synchronization */
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}
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/* ----------------------------------------------------------------------------------------------
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* 3) Put Generic Clock Generator 1 as source for Generic Clock Multiplexer 0 (DFLL48M reference)
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*/
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GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID( GENERIC_CLOCK_MULTIPLEXER_DFLL48M ) | // Generic Clock Multiplexer 0
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GCLK_CLKCTRL_GEN_GCLK1 | // Generic Clock Generator 1 is source
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GCLK_CLKCTRL_CLKEN;
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while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
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{
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/* Wait for synchronization */
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}
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/* ----------------------------------------------------------------------------------------------
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* 4) Enable DFLL48M clock
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*/
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/* DFLL Configuration in Closed Loop mode, cf product datasheet chapter 15.6.7.1 - Closed-Loop Operation */
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/* Remove the OnDemand mode, Bug http://avr32.icgroup.norway.atmel.com/bugzilla/show_bug.cgi?id=9905 */
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SYSCTRL->DFLLCTRL.bit.ONDEMAND = 0;
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while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLRDY) == 0 )
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{
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/* Wait for synchronization */
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}
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SYSCTRL->DFLLMUL.reg = SYSCTRL_DFLLMUL_CSTEP( 31 ) | // Coarse step is 31, half of the max value
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SYSCTRL_DFLLMUL_FSTEP( 511 ) | // Fine step is 511, half of the max value
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SYSCTRL_DFLLMUL_MUL( (VARIANT_MCK/VARIANT_MAINOSC) ); // External 32KHz is the reference
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while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLRDY) == 0 )
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{
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/* Wait for synchronization */
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}
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/* Write full configuration to DFLL control register */
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SYSCTRL->DFLLCTRL.reg |= SYSCTRL_DFLLCTRL_MODE | /* Enable the closed loop mode */
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SYSCTRL_DFLLCTRL_WAITLOCK |
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SYSCTRL_DFLLCTRL_QLDIS; /* Disable Quick lock */
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while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLRDY) == 0 )
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{
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/* Wait for synchronization */
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}
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/* Enable the DFLL */
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SYSCTRL->DFLLCTRL.reg |= SYSCTRL_DFLLCTRL_ENABLE;
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while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLLCKC) == 0 ||
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(SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLLCKF) == 0 )
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{
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/* Wait for locks flags */
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}
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while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLRDY) == 0 )
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{
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/* Wait for synchronization */
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}
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/* ----------------------------------------------------------------------------------------------
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* 5) Switch Generic Clock Generator 0 to DFLL48M. CPU will run at 48MHz.
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*/
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GCLK->GENDIV.reg = GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_MAIN ); // Generic Clock Generator 0
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while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
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{
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/* Wait for synchronization */
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}
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/* Write Generic Clock Generator 0 configuration */
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GCLK->GENCTRL.reg = GCLK_GENCTRL_ID( GENERIC_CLOCK_GENERATOR_MAIN ) | // Generic Clock Generator 0
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GCLK_GENCTRL_SRC_DFLL48M | // Selected source is DFLL 48MHz
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// GCLK_GENCTRL_OE | // Output clock to a pin for tests
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GCLK_GENCTRL_IDC | // Set 50/50 duty cycle
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GCLK_GENCTRL_GENEN;
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while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
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{
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/* Wait for synchronization */
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}
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#if 0
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/* ----------------------------------------------------------------------------------------------
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* 6) Modify PRESCaler value of OSC8M to have 8MHz
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*/
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SYSCTRL->OSC8M.bit.PRESC = SYSCTRL_OSC8M_PRESC_1_Val;
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SYSCTRL->OSC8M.bit.ONDEMAND = 0;
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/* ----------------------------------------------------------------------------------------------
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* 7) Put OSC8M as source for Generic Clock Generator 3
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*/
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GCLK->GENDIV.reg = GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_OSC8M ); // Generic Clock Generator 3
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/* Write Generic Clock Generator 3 configuration */
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GCLK->GENCTRL.reg = GCLK_GENCTRL_ID( GENERIC_CLOCK_GENERATOR_OSC8M ) | // Generic Clock Generator 3
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GCLK_GENCTRL_SRC_OSC8M | // Selected source is RC OSC 8MHz (already enabled at reset)
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// GCLK_GENCTRL_OE | // Output clock to a pin for tests
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GCLK_GENCTRL_GENEN;
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while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
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{
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/* Wait for synchronization */
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}
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#endif //0
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/*
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* Now that all system clocks are configured, we can set CPU and APBx BUS clocks.
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* These values are normally the ones present after Reset.
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*/
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PM->CPUSEL.reg = PM_CPUSEL_CPUDIV_DIV1;
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PM->APBASEL.reg = PM_APBASEL_APBADIV_DIV1_Val;
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PM->APBBSEL.reg = PM_APBBSEL_APBBDIV_DIV1_Val;
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PM->APBCSEL.reg = PM_APBCSEL_APBCDIV_DIV1_Val;
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}
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