machine_cycle.c

用quartusII编写的

#include "..\..\includes.h"


//------------------------------------------------------------------------
// 设置一个机器周期由多少个振荡周期组成
//------------------------------------------------------------------------
void SetClocksPerMachineCycle( INT16U ClocksPerMachineCycle )
{
      INT8U mask;
      
      mask = PMR;
      
      mask &= ~(3<<6);
      
      if( ClocksPerMachineCycle == 4 )
      {
            mask |= (1<<6);
      }
      else if( ClocksPerMachineCycle == 64 )
      {
            // 要切换到clock/64和clock/1024模式，必须首先切换到clock/4模式
            mask |= (1<<6);
            PMR = mask;
                  
            mask &= ~(3<<6);
            mask |= (2<<6);
      }
      else if( ClocksPerMachineCycle == 1024 )
      {
            // 要切换到clock/64和clock/1024模式，必须首先切换到clock/4模式
            mask |= (1<<6);
            PMR = mask;
                  
            mask &= ~(3<<6);
            mask |= (3<<6);
      }
      else
      {     // 如果是不合理的ClocksPerMachineCycle值，则切换到clock/4模式
            mask |= (1<<6);
      } 
      
      PMR = mask;
}