CPUCS = ((CPUCS & ~bmCLKSPD) | bmCLKSPD1)

  这里的(CPUCS&~bmCLKSPD)|bmCLKSPD1 是什么意思呢
请高手指教

void TD_Init(void)             // Called once at startup
{
   // set the CPU clock to 48MHz

   CPUCS = ((CPUCS & ~bmCLKSPD) | bmCLKSPD1) ;

   // set the slave FIFO interface to 48MHz
   IFCONFIG |= 0x40;

  // Registers which require a synchronization delay, see section 15.14
  // FIFORESET        FIFOPINPOLAR
  // INPKTEND         OUTPKTEND
  // EPxBCH:L         REVCTL
  // GPIFTCB3         GPIFTCB2
  // GPIFTCB1         GPIFTCB0
  // EPxFIFOPFH:L     EPxAUTOINLENH:L
  // EPxFIFOCFG       EPxGPIFFLGSEL
  // PINFLAGSxx       EPxFIFOIRQ
  // EPxFIFOIE        GPIFIRQ
  // GPIFIE           GPIFADRH:L
  // UDMACRCH:L       EPxGPIFTRIG
  // GPIFTRIG
  
  // Note: The pre-REVE EPxGPIFTCH/L register are affected, as well...
  //      ...these have been replaced by GPIFTC[B3:B0] registers

  // default: all endpoints have their VALID bit set
  // default: TYPE1 = 1 and TYPE0 = 0 --> BULK  
  // default: EP2 and EP4 DIR bits are 0 (OUT direction)
  // default: EP6 and EP8 DIR bits are 1 (IN direction)
  // default: EP2, EP4, EP6, and EP8 are double buffered

  // we are just using the default values, yes this is not necessary...
  EP1OUTCFG = 0xA0;
  EP1INCFG = 0xA0;
  SYNCDELAY;                    // see TRM section 15.14
  EP2CFG = 0xA2;
  SYNCDELAY;                    
  EP4CFG = 0xA0;
  SYNCDELAY;                    
  EP6CFG = 0xE2;
  SYNCDELAY;                    
  EP8CFG = 0xE0;

  // out endpoints do not come up armed
  
  // since the defaults are double buffered we must write dummy byte counts twice
  SYNCDELAY;                    
  EP2BCL = 0x80;                // arm EP2OUT by writing byte count w/skip.
  SYNCDELAY;                    
  EP2BCL = 0x80;
  SYNCDELAY;                    
  EP4BCL = 0x80;                // arm EP4OUT by writing byte count w/skip.
  SYNCDELAY;                    
  EP4BCL = 0x80;    

  // enable dual autopointer feature
  AUTOPTRSETUP |= 0x01;

  Rwuen = TRUE;                 // Enable remote-wakeup
}