tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_Maxim/TARGET_MAX32600/TARGET_MAX32600MBED/low_level_init.c

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  32  */
  33
  34 #include "cmsis.h"
  35 #include "gpio_regs.h"
  36 #include "clkman_regs.h"
  37
  38 /* Application developer should override where necessary with different external HFX source */
  39 #ifndef __SYSTEM_HFX
  40 #define __SYSTEM_HFX 24000000
  41 #endif
  42
  43 //******************************************************************************
  44 // This function will get called early in system initialization
  45 void low_level_init(void)
  46 {
  47     /* wait for the RO to stabilize */
  48     while (!(MXC_CLKMAN->intfl & MXC_F_CLKMAN_INTFL_RING_STABLE));
  49
  50     /* Configure and enable the oscillator */
  51     if (!(MXC_CLKMAN->clk_config & MXC_F_CLKMAN_CLK_CONFIG_HFX_ENABLE)) {
  52
  53         MXC_CLKMAN->clk_config = (0x4 << MXC_F_CLKMAN_CLK_CONFIG_HFX_GM_ADJUST_POS);
  54
  55         /* Enable the external crystal */
  56         MXC_CLKMAN->clk_config |= MXC_F_CLKMAN_CLK_CONFIG_HFX_ENABLE;
  57     }
  58
  59     /* Wait for external crystal to stabilize */
  60     for (volatile int waitcnt = 0; waitcnt < 0x4000; waitcnt++);    // 0x4000 ~10ms 0x10000 ~35ms, 0x20000 ~75ms
  61
  62     /* Configure the PLL */
  63     uint32_t clk_config = MXC_CLKMAN->clk_config;
  64     clk_config  = (clk_config & ~MXC_F_CLKMAN_CLK_CONFIG_PLL_INPUT_SELECT) | (MXC_E_CLKMAN_PLL_INPUT_SELECT_HFX << MXC_F_CLKMAN_CLK_CONFIG_PLL_INPUT_SELECT_POS);
  65
  66 #if (__SYSTEM_HFX == 8000000)
  67     clk_config  = (clk_config & ~MXC_F_CLKMAN_CLK_CONFIG_PLL_DIVISOR_SELECT) | (MXC_E_CLKMAN_PLL_DIVISOR_SELECT_8MHZ << MXC_F_CLKMAN_CLK_CONFIG_PLL_DIVISOR_SELECT_POS);
  68 #elif (__SYSTEM_HFX == 12000000)
  69     clk_config  = (clk_config & ~MXC_F_CLKMAN_CLK_CONFIG_PLL_DIVISOR_SELECT) | (MXC_E_CLKMAN_PLL_DIVISOR_SELECT_12MHZ << MXC_F_CLKMAN_CLK_CONFIG_PLL_DIVISOR_SELECT_POS);
  70 #elif (__SYSTEM_HFX == 24000000)
  71     clk_config  = (clk_config & ~MXC_F_CLKMAN_CLK_CONFIG_PLL_DIVISOR_SELECT) | (MXC_E_CLKMAN_PLL_DIVISOR_SELECT_24MHZ << MXC_F_CLKMAN_CLK_CONFIG_PLL_DIVISOR_SELECT_POS);
  72 #else
  73 #error Invalid __SYSTEM_HFX setting
  74 #endif
  75
  76     clk_config |=  MXC_F_CLKMAN_CLK_CONFIG_PLL_8MHZ_ENABLE;
  77     clk_config &= ~MXC_F_CLKMAN_CLK_CONFIG_PLL_BYPASS;
  78     clk_config  = (clk_config & ~MXC_F_CLKMAN_CLK_CONFIG_PLL_STABILITY_COUNT) | (MXC_E_CLKMAN_STABILITY_COUNT_2_13_CLKS << MXC_F_CLKMAN_CLK_CONFIG_PLL_STABILITY_COUNT_POS);
  79     MXC_CLKMAN->clk_config = clk_config;
  80
  81     /* Enable the PLL and wait for stable */
  82     MXC_CLKMAN->clk_config |= (MXC_F_CLKMAN_CLK_CONFIG_PLL_ENABLE | MXC_F_CLKMAN_CLK_CONFIG_PLL_RESET_N);
  83     while (!(MXC_CLKMAN->intfl & MXC_F_CLKMAN_INTFL_PLL_STABLE));
  84
  85     /* Switch to the PLL */
  86     MXC_CLKMAN->clk_ctrl = (MXC_CLKMAN->clk_ctrl & ~MXC_F_CLKMAN_CLK_CTRL_SYSTEM_SOURCE_SELECT) |
  87                            ((MXC_E_CLKMAN_SYSTEM_SOURCE_SELECT_PLL_48MHZ_DIV_2 << MXC_F_CLKMAN_CLK_CTRL_SYSTEM_SOURCE_SELECT_POS));
  88 }