官方程序的学习

在msp430F5529的官方程序中，在对主时钟设置为25M时为什么要采用这个程序呢？好像是提升内部电压，是为了防止程序跑飞吗？谢谢

那么430 主时钟设置为多少M时需要考虑用PMM模块？

void SetVcoreUp (unsigned int level)
{
                                                                             // Open PMM registers for write
  PMMCTL0_H = PMMPW_H;             
                                                                       // Set SVS/SVM high side new level
  SVSMHCTL = SVSHE + SVSHRVL0 * level + SVMHE + SVSMHRRL0 * level;
                                                                                // Set SVM low side to new level
  SVSMLCTL = SVSLE + SVMLE + SVSMLRRL0 * level;
                                                                                    // Wait till SVM is settled
  while ((PMMIFG & SVSMLDLYIFG) == 0);
                                                                         // Clear already set flags
  PMMIFG &= ~(SVMLVLRIFG + SVMLIFG);
                                                                         // Set VCore to new level
  PMMCTL0_L = PMMCOREV0 * level;
                                                                              // Wait till new level reached
  if ((PMMIFG & SVMLIFG))
    while ((PMMIFG & SVMLVLRIFG) == 0);
                                                                               // Set SVS/SVM low side to new level
  SVSMLCTL = SVSLE + SVSLRVL0 * level + SVMLE + SVSMLRRL0 * level;
                                                                                         // Lock PMM registers for write access
  PMMCTL0_H = 0x00;
}