[应用相关] 系统时钟初始化at32f4xx_clock.c中HEXT启动说明

#define HEXT_STABLE_DELAY (5000u)

#define PLL_STABLE_DELAY (500u)

/* reset crm */

crm_reset();

crm_clock_source_enable(CRM_CLOCK_SOURCE_HEXT, TRUE);

<font color="#ff0000">/* wait for hext stable ,specially for AT32F403*/

wait_stbl(HEXT_STABLE_DELAY);</font>

/* wait till hext is ready */

while(crm_hext_stable_wait() == ERROR)

{

}

/* config pll clock resource */

crm_pll_config(CRM_PLL_SOURCE_HEXT_DIV, CRM_PLL_MULT_48, CRM_PLL_OUTPUT_RANGE_GT72MHZ);

/* enable pll */

crm_clock_source_enable(CRM_CLOCK_SOURCE_PLL, TRUE);

/* wait till pll is ready */

while(crm_flag_get(CRM_PLL_STABLE_FLAG) != SET)

{

}

/* config apb2clk */

crm_apb2_div_set(CRM_APB2_DIV_2);

/* config apb1clk */

crm_apb1_div_set(CRM_APB1_DIV_2);

/* 1step: config ahbclk div8 */

crm_ahb_div_set(CRM_AHB_DIV_8);

/* select pll as system clock source */

crm_sysclk_switch(CRM_SCLK_PLL);

/* wait till pll is used as system clock source */

while(crm_sysclk_switch_status_get() != CRM_SCLK_PLL)

#define HEXT_STARTUP_TIMEOUT ((uint16_t)0x3000) /*!< time out for hext start up */

error_status crm_hext_stable_wait(void)

{

 uint32_t stable_cnt = 0;

 error_status status = ERROR;

 while((crm_flag_get(CRM_HEXT_STABLE_FLAG) != SET) && (stable_cnt < HEXT_STARTUP_TIMEOUT))

 {

 stable_cnt ++;

 }

 if(crm_flag_get(CRM_HEXT_STABLE_FLAG) != SET)

 {

 status = ERROR;

 }

 else

 {

 status = SUCCESS;

 }

 return status;

}