| //***************************************************************************** |
| // |
| //! @file system_apollo2.c |
| //! |
| //! @brief Ambiq Micro Apollo2 MCU specific functions. |
| // |
| //***************************************************************************** |
| |
| //***************************************************************************** |
| // |
| // Copyright (c) 2017, Ambiq Micro |
| // 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 the copyright holder nor the names of its |
| // contributors 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. |
| // |
| //***************************************************************************** |
| |
| #include <stdint.h> |
| #include "mcu/system_apollo2.h" |
| #include "mcu/apollo2.h" |
| #include "mcu/cmsis_nvic.h" |
| |
| //***************************************************************************** |
| // |
| // Defines |
| // |
| //***************************************************************************** |
| |
| // |
| // Clocks |
| // |
| #define __HSI (6000000UL) |
| #define __XTAL (32768UL) // Crystal Oscillator frequency |
| #define __SYS_OSC_CLK (48000000) // Main oscillator frequency |
| #define __SYSTEM_CLOCK (1*__SYS_OSC_CLK) |
| |
| // |
| // Initialize SystemCoreClock with the system core clock frequency value |
| // achieved after system intitialization. |
| // This means system core clock frequency after call to SystemInit() |
| // |
| uint32_t SystemCoreClock = __SYSTEM_CLOCK; // System Clock Frequency (Core Clock) |
| |
| //***************************************************************************** |
| // |
| //! @brief Set the global clock frequncy. |
| //! |
| //! This function sets the global clock frequency. |
| //! |
| //! @return None. |
| // |
| //***************************************************************************** |
| void |
| SystemCoreClockUpdate(void) |
| { |
| // |
| // Calculate the system frequency based upon the current register settings. |
| // This function can be used to retrieve the system core clock frequeny |
| // after user changed register sittings. |
| // |
| SystemCoreClock = __SYS_OSC_CLK / (CLKGEN->CCTRL_b.CORESEL + 1); |
| } |
| |
| //***************************************************************************** |
| // |
| //! @brief Initialize the system. |
| //! |
| //! This function sets up the microcontroller system. |
| //! |
| //! @return None. |
| // |
| //***************************************************************************** |
| void |
| SystemInit(void) |
| { |
| // |
| // Initialize the system |
| // Do not use global variables because this function is called before |
| // reaching pre-main. RW section maybe overwritten afterwards. |
| // |
| SystemCoreClock = __SYSTEM_CLOCK; |
| |
| CLKGEN->CLKKEY = 0x47; // Enable write to CCTRL |
| CLKGEN->CCTRL_b.CORESEL = 0; // Div by 1 for 48MHz |
| CLKGEN->CLKKEY = 0; // Disable write to CCTRL |
| |
| SystemCoreClockUpdate(); |
| |
| NVIC_Relocate(); |
| } |
| |
