LPC1768 CPU 時鐘配置

#if (CLOCK_SETUP)
LPC_SC->SCS = SCS_Val;// 啟用外部主時鐘
if (SCS_Val & (1 << 5)) {
while ((LPC_SC->SCS & (1<<6)) == 0);
}

//PLL倍頻出來的時鐘送給CPU前的分頻，CCLKCFG_Val=3，為4分頻

LPC_SC->CCLKCFG = CCLKCFG_Val;

LPC_SC->PCLKSEL0 = PCLKSEL0_Val;
LPC_SC->PCLKSEL1 = PCLKSEL1_Val;

LPC_SC->CLKSRCSEL = CLKSRCSEL_Val;

#if (PLL0_SETUP)

//PLL0CFG_Val = 0x00050063，5為pre-div的值既N，所以除數為N+1=6

// 0x63為乘數M，M+1=100，記得要把16進制換算為10進制

//Fcco = 2*100*12/6 = 400，然后再除以CPU clock的4，即該設置主頻為100M
LPC_SC->PLL0CFG = PLL0CFG_Val;
LPC_SC->PLL0CON = 0x01;

//確認序列
LPC_SC->PLL0FEED = 0xAA;
LPC_SC->PLL0FEED = 0x55;
while (!(LPC_SC->PLL0STAT & (1<<26)));

LPC_SC->PLL0CON = 0x03;
LPC_SC->PLL0FEED = 0xAA;
LPC_SC->PLL0FEED = 0x55;
#endif

#if (PLL1_SETUP)
LPC_SC->PLL1CFG = PLL1CFG_Val;
LPC_SC->PLL1CON = 0x01;
LPC_SC->PLL1FEED = 0xAA;
LPC_SC->PLL1FEED = 0x55;
while (!(LPC_SC->PLL1STAT & (1<<10)));

LPC_SC->PLL1CON = 0x03;
LPC_SC->PLL1FEED = 0xAA;
LPC_SC->PLL1FEED = 0x55;
#else
LPC_SC->USBCLKCFG = USBCLKCFG_Val;
#endif

LPC_SC->PCONP = PCONP_Val;

LPC_SC->CLKOUTCFG = CLKOUTCFG_Val;
#endif

if (((LPC_SC->PLL0STAT >> 24)&3)==3) {
switch (LPC_SC->CLKSRCSEL & 0x03) {
case 0:
case 3:
SystemFrequency = (IRC_OSC *
((2 * ((LPC_SC->PLL0STAT & 0x7FFF) + 1))) /
(((LPC_SC->PLL0STAT >> 16) & 0xFF) + 1) /
((LPC_SC->CCLKCFG & 0xFF)+ 1));
break;
case 1:

//待Pll鎖定和連接后PLL0STAT中有M和N，可以計算出實際頻率
SystemFrequency = (OSC_CLK *
((2 * ((LPC_SC->PLL0STAT & 0x7FFF) + 1))) /
(((LPC_SC->PLL0STAT >> 16) & 0xFF) + 1) /
((LPC_SC->CCLKCFG & 0xFF)+ 1));
break;
case 2:
SystemFrequency = (RTC_CLK *
((2 * ((LPC_SC->PLL0STAT & 0x7FFF) + 1))) /
(((LPC_SC->PLL0STAT >> 16) & 0xFF) + 1) /
((LPC_SC->CCLKCFG & 0xFF)+ 1));
break;
}
} else {
switch (LPC_SC->CLKSRCSEL & 0x03) {
case 0:
case 3:
SystemFrequency = IRC_OSC / ((LPC_SC->CCLKCFG & 0xFF)+ 1);
break;
case 1:
SystemFrequency = OSC_CLK / ((LPC_SC->CCLKCFG & 0xFF)+ 1);
break;
case 2:
SystemFrequency = RTC_CLK / ((LPC_SC->CCLKCFG & 0xFF)+ 1);
break;
}
}