mirror of https://github.com/ARMmbed/mbed-os.git
93 lines
3.5 KiB
C
93 lines
3.5 KiB
C
/* mbed Microcontroller Library
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* Copyright (c) 2015-2017 Nuvoton
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "cmsis.h"
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void mbed_sdk_init(void)
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{
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// NOTE: Support singleton semantics to be called from other init functions
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static int inited = 0;
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if (inited) {
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return;
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}
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inited = 1;
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/*---------------------------------------------------------------------------------------------------------*/
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/* Init System Clock */
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/*---------------------------------------------------------------------------------------------------------*/
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/* Unlock protected registers */
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SYS_UnlockReg();
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/* Enable HIRC clock (internal OSC 12MHz) */
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CLK_EnableXtalRC(CLK_PWRCTL_HIRC_EN_Msk);
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/* Enable HXT clock (external XTAL 12MHz) */
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CLK_EnableXtalRC(CLK_PWRCTL_HXT_EN_Msk);
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/* Enable LIRC clock (OSC 10KHz) for lp_ticker */
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CLK_EnableXtalRC(CLK_PWRCTL_LIRC_EN_Msk);
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/* Enable LXT clock (XTAL 32KHz) for RTC */
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CLK_EnableXtalRC(CLK_PWRCTL_LXT_EN_Msk);
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/* Wait for HIRC clock ready */
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CLK_WaitClockReady(CLK_CLKSTATUS_HIRC_STB_Msk);
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/* Wait for HXT clock ready */
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CLK_WaitClockReady(CLK_CLKSTATUS_HXT_STB_Msk);
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/* Wait for LIRC clock ready */
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CLK_WaitClockReady(CLK_CLKSTATUS_LIRC_STB_Msk);
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/* Wait for LXT clock ready */
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CLK_WaitClockReady(CLK_CLKSTATUS_LXT_STB_Msk);
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/* Set HCLK source form HXT and HCLK source divide 1 */
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CLK_SetHCLK(CLK_CLKSEL0_HCLK_S_HXT, CLK_HCLK_CLK_DIVIDER(1));
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/* Select HXT/HIRC to clock PLL
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*
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* Comparison between HXT/HIRC-clocked PLL:
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* 1. Spare HXT on board if only HIRC is used.
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* 2. HIRC has shorter stable time.
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* 3. HXT has better accuracy. USBD requires HXT-clocked PLL.
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* 4. HIRC has shorter wake-up time from power-down mode.
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* Per test, wake-up time from power-down mode would take:
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* T1. 1~13 ms (proportional to deep sleep time) with HXT-clocked PLL as HCLK clock source
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* T2. <1 ms with HIRC-clocked PLL as HCLK clock source
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* T1 will fail Greentea test which requires max 10 ms wake-up time.
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*
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* If we just call CLK_SetCoreClock(FREQ_48MHZ) to configure HCLK to 48 MHz,
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* it will go T1 with HXT already enabled in front. So we manually configure
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* it to choose HXT/HIRC-clocked PLL.
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*/
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#define NU_HXT_PLL 1
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#define NU_HIRC_PLL 2
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#ifndef NU_CLOCK_PLL
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#define NU_CLOCK_PLL NU_HIRC_PLL
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#endif
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#if (NU_CLOCK_PLL == NU_HXT_PLL)
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CLK_EnablePLL(CLK_PLLCTL_PLL_SRC_HXT, FREQ_48MHZ*2);
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CLK_SetHCLK(CLK_CLKSEL0_HCLK_S_PLL, CLK_HCLK_CLK_DIVIDER(2));
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#elif (NU_CLOCK_PLL == NU_HIRC_PLL)
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CLK_EnablePLL(CLK_PLLCTL_PLL_SRC_HIRC, FREQ_48MHZ*2);
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CLK_SetHCLK(CLK_CLKSEL0_HCLK_S_PLL, CLK_HCLK_CLK_DIVIDER(2));
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#endif
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/* Update System Core Clock */
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/* User can use SystemCoreClockUpdate() to calculate SystemCoreClock. */
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SystemCoreClockUpdate();
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/* Lock protected registers */
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SYS_LockReg();
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}
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