Datasheet

LPC11U1X All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 2.2 — 11 March 2014 24 of 72
NXP Semiconductors
LPC11U1x
32-bit ARM Cortex-M0 microcontroller
7.16.1.1 Internal RC oscillator
The IRC may be used as the clock source for the WDT, and/or as the clock that drives the
system PLL and subsequently the CPU. The nominal IRC frequency is 12 MHz.
Upon power-up, any chip reset, or wake-up from Deep power-down mode, the LPC11U1x
use the IRC as the clock source. Software may later switch to one of the other available
clock sources.
Fig 6. LPC11U1x clocking generation block diagram
system oscillator
watchdog oscillator
IRC oscillator
USB PLL
USBPLLCLKSEL
(USB clock select)
SYSTEM CLOCK
DIVIDER
SYSAHBCLKCTRLn
(AHB clock enable)
CPU, system control,
PMU
memories,
peripheral clocks
SSP0 PERIPHERAL
CLOCK DIVIDER
SSP0
SSP1 PERIPHERAL
CLOCK DIVIDER
SSP1
USART PERIPHERAL
CLOCK DIVIDER
UART
WDT
WDCLKSEL
(WDT clock select)
USB 48 MHz CLOCK
DIVIDER
USB
USBUEN
(USB clock update enable)
watchdog oscillator
IRC oscillator
system oscillator
CLKOUT PIN CLOCK
DIVIDER
CLKOUT pin
CLKOUTUEN
(CLKOUT update enable)
002aaf892
system clock
SYSTEM PLL
IRC oscillator
system oscillator
watchdog oscillator
MAINCLKSEL
(main clock select)
SYSPLLCLKSEL
(system PLL clock select)
main clock
IRC oscillator
n