2812的为啥倍频不起作用

pppphzmns

2812的为啥倍频不起作用 [复制链接]

2812采用30MHz晶振，5倍频，时钟应是150M，但实际上倍频没有作用，时钟还是30M，请问可能的原因在哪儿。还有就是DSP2812的140脚XF_PLL的引脚应该怎么接

eestudent

望EEWORLD的老师指点一下

bailicai

倍频要在程序里倍啊。。
// This function initializes the PLLCR register.
void Init_Pll(UINT val)
{
   volatile Uint16 iVol;
   PllVal = (val/2);   
   
   if (*SYSCTRL_REG_PLLCR != val)
   {
   
      EALLOW;
      *SYSCTRL_REG_PLLCR = val;
      EDIS;
   
   // Optional: Wait for PLL to lock.
   // During this time the CPU will switch to OSCCLK/2 until the PLL is
   // stable.  Once the PLL is stable the CPU will switch to the new PLL value.
   //
   // This switch time is 131072 CLKIN cycles as of Rev C silicon.  
   //   
   // Code is not required to sit and wait for the PLL to lock.   
   // However, if the code does anything that is timing critical,
   // and requires the correct clock be locked, then it is best to
   // wait until this switching has completed.  
   
   // If this function is run from waitstated memory, then the loop count can
   // be reduced as long as the minimum switch time is still met.

   // iVol is volatile so the compiler will not optimize this loop out
   //
   // The watchdog should be disabled before this loop, or fed within
   // the loop.   
   
      DisableDog();
   
   // Wait lock cycles.  
   // Note,  This loop is tuned to 0-waitstate RAM memory.  If this
   // function is run from wait-stated memory such as Flash or XINTF,
   // then the number of times through the loop can be reduced
   // accordingly.
      for(iVol= 0; iVol< ( (131072/2)/12 ); iVol++)
      {
   
      }
   }
}

mbb

那XF_PLL的引脚应该怎么接呢？下拉到地吗？我用的是外部时钟源，X1和X2引脚间接了30MHz的晶体。

rainchencxy

我就是在程序中进行5倍频，同样是进行程序延时，但不起作用，后来加上外部看门狗后，时钟恢复正常，150M。怀疑是没有看门狗时，DSP对PLL管脚采样不正常引起的。

bluejb119

我就是在程序中进行5倍频，同样是进行程序延时，但不起作用，后来加上外部看门狗后，时钟恢复正常，150M。怀疑是没有看门狗时，DSP对PLL管脚采样不正常引起的。