Disable PLL

[lpcware]

Content originally posted in LPCWare by cksa361 on Sun Dec 05 13:16:36 MST 2010
Is it possible to be in Active mode with the PLL disabled, so that the core is running straight off the 12Mhz Crystal?

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Sun Dec 05 23:58:21 MST 2010
Use something like:

[LEFT]LPC_SYSCON->PDRUNCFG &= ~(1 << 5); //Power-up System Osc
LPC_SYSCON->SYSOSCCTRL = 1; //bypass PLL[/LEFT]
 
[LEFT]LPC_SYSCON->MAINCLKSEL = 1; //Select PLL Clock init
LPC_SYSCON->MAINCLKUEN = 0x01; //Update MCLK Clock Source
LPC_SYSCON->MAINCLKUEN = 0x00; //Toggle Update Register
LPC_SYSCON->MAINCLKUEN = 0x01;[/LEFT]
while (!(LPC_SYSCON->MAINCLKUEN & 0x01)); //Wait Until Updated

[lpcware]

Content originally posted in LPCWare by gbm on Sun Dec 05 16:37:41 MST 2010
Of course it is. Right after reset LPC1xxx operates from internal RC oscillator. You may switch to crystal oscillator without activating PLL. Read the section on clocking in your chip manual. So far in all my LPC1111 projects I use IRC clock without PLL.