【极海APM32F407 Tiny Board】4、DWT实现延时函数

dql2016

【极海APM32F407 Tiny Board】4、DWT实现延时函数 [复制链接]

 

uint32_t delay_init(void) 
{
	uint32_t c;

	/* Enable TRC */
	CoreDebug->DEMCR &= ~0x01000000;
	CoreDebug->DEMCR |=  0x01000000;

	/* Enable counter */
	DWT->CTRL &= ~0x00000001;
	DWT->CTRL |=  0x00000001;

	/* Reset counter */
	DWT->CYCCNT = 0;

	/* Check if DWT has started */
	c = DWT->CYCCNT;

	/* 2 dummys */
	__ASM volatile ("NOP");
	__ASM volatile ("NOP");

	/* Return difference, if result is zero, DWT has not started */
	return (DWT->CYCCNT - c);
}

void delay_us(uint32_t us) 
{
	uint32_t start = DWT->CYCCNT;
	/* Go to number of cycles for system */
	us *= (SystemCoreClock / 1000000);
	/* Delay till end */
	while ((DWT->CYCCNT - start) < us);
}

void delay_ms(uint32_t ms) 
{
	uint32_t start = DWT->CYCCNT;
	/* Go to number of cycles for system */
	ms *= (SystemCoreClock / 1000);
	/* Delay till end */
	while ((DWT->CYCCNT - start) < ms);
}

DWT外设是M4内核的特性之一。

lugl4313820

• __ASM volatile ("NOP");
• __ASM volatile ("NOP");

大佬这就上ASM代码呀

damiaa

DWT外设 感谢分享

dql2016

lugl4313820 发表于 2023-5-26 07:02 __ASM volatile ("NOP"); __ASM volatile ("NOP"); 大佬这就上ASM代码呀

lugl4313820

看到大佬用汇编，就有高大上的感觉，太牛了。