1 /*******************************************************************************
2 * Copyright (C) 2015 Maxim Integrated Products, Inc., All Rights Reserved.
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31 *******************************************************************************
35 #include "gpio_regs.h"
36 #include "clkman_regs.h"
38 /* Application developer should override where necessary with different external HFX source */
40 #define __SYSTEM_HFX 24000000
43 //******************************************************************************
44 // This function will get called early in system initialization
45 void low_level_init(void)
47 /* wait for the RO to stabilize */
48 while (!(MXC_CLKMAN
->intfl
& MXC_F_CLKMAN_INTFL_RING_STABLE
));
50 /* Configure and enable the oscillator */
51 if (!(MXC_CLKMAN
->clk_config
& MXC_F_CLKMAN_CLK_CONFIG_HFX_ENABLE
)) {
53 MXC_CLKMAN
->clk_config
= (0x4 << MXC_F_CLKMAN_CLK_CONFIG_HFX_GM_ADJUST_POS
);
55 /* Enable the external crystal */
56 MXC_CLKMAN
->clk_config
|= MXC_F_CLKMAN_CLK_CONFIG_HFX_ENABLE
;
59 /* Wait for external crystal to stabilize */
60 for (volatile int waitcnt
= 0; waitcnt
< 0x4000; waitcnt
++); // 0x4000 ~10ms 0x10000 ~35ms, 0x20000 ~75ms
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
);
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
);
73 #error Invalid __SYSTEM_HFX setting
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
;
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
));
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
));