学习KEA之时钟

我们以KEA64系列来学习时钟， 其中KEA64系列包括：

• SKEAZN16AMLC®
• SKEAZN32AMLC®
• SKEAZN64AMLC®
• SKEAZN32AMLH®
• SKEAZN64AMLH®

其它系列的和KEA64类似，但也有点不同，具体要看各自的参考手册。

时钟框图

片上有三种时钟源模块:

• Internal Clock Source (ICS) module:
  • The main clock source generator providing bus clock and other reference clocks to peripherals
• System Oscillator (OSC) module:
  • The system oscillator providing reference clock to internal clock source (ICS), the real-time clock counter clock module (RTC), and other MCU sub-systems
• Low-Power Oscillator (LPO) module:
  • The on-chip low-power oscillator providing 1 kHz reference clock to RTC and Watchdog (WDOG)
    
    

配置内部时钟

我们以内部晶振为例，最终目标是：

• Core Clock to 40MHz
• Bus Clock to 20MHz
• BUSOUT to 156.25 KHz

/***********************************************************************************************
*
* @brief    CLK_Init - Initialize Core Clock to 40MHz, Bus Clock to 20MHz
* @param    none
* @return   none
*
************************************************************************************************/
void Clk_Init(void)
{
	OSC_CR = 0x00;      /* (default value) */
						/* OSCEN=0: OSC module disabled */
						/* OSCSTEN=0: OSC clock disabled in Stop mode */
						/* OSCOS=0: Ext clk source (don't care here) */
						/* RANGE=0: Low Freq range of 32 KHz */
						/* HGO=0: low power High Gan Osc mode (don't care here) */

	 ICS_C1 |= ICS_C1_IRCLKEN_MASK; /* Enable the internal reference clock*/
	 ICS_C3= 0x50; /* Reference clock frequency =  39.0625 kHz*/

	 while(!(ICS_S & ICS_S_LOCK_MASK)); /* Wait for PLL lock, now running at 40 MHz (1024*39.0625 kHz) */

	 ICS_C2|=ICS_C2_BDIV(1) ; /*BDIV=2, Bus clock = 20 MHz*/
	 ICS_S |= ICS_S_LOCK_MASK ; /* Clear Loss of lock sticky bit */
}

int main(void)
{
	SIM_SOPT |= SIM_SOPT_CLKOE_MASK | SIM_SOPT_BUSREF(0b111); /*Enable BUSOUT on PTH2, Bus clock divided by 128 */
	
	Clk_Init();

	for(;;)
	{
		;
	}
}

运行程序后，可以在PTH2/BUSOUT(Pin6)中察看输出的BUS分频时钟：20 MHz / 128 = 156.25 KHz:

注：我这里实际是161.3 KHz，有点点偏差

持续更新