Datasheet

Table Of Contents
LPC11CX2_CX4 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 3.1 — 15 May 2013 23 of 62
NXP Semiconductors
LPC11Cx2/Cx4
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
PLL and subsequently the CPU. The nominal IRC frequency is 12 MHz. The IRC is
trimmed to 1 % accuracy over the entire voltage and temperature range.
Upon power-up or any chip reset, the LPC11Cx2/Cx4 use the IRC as the clock source.
Software may later switch to one of the other available clock sources.
7.16.1.2 System oscillator
The system oscillator can be used as the clock source for the CPU, with or without using
the PLL.
The system oscillator operates at frequencies of 1 MHz to 25 MHz. This frequency can be
boosted to a higher frequency, up to the maximum CPU operating frequency, by the
system PLL.
Fig 5. LPC11Cx2/Cx4 clock generation block diagram
SYSTEM PLL
IRC oscillator
system oscillator
watchdog oscillator
IRC oscillator
watchdog oscillator
MAINCLKSEL
(main clock select)
SYSPLLCLKSEL
(system PLL clock select)
SYSTEM CLOCK
DIVIDER
AHB clock 0
(system)
SYSAHBCLKCTRL[1:18]
(AHB clock enable)
AHB clocks 1 to 18
(memories
and peripherals)
SPI0 PERIPHERAL
CLOCK DIVIDER
SPI0
SPI1 PERIPHERAL
CLOCK DIVIDER
SPI1
UART PERIPHERAL
CLOCK DIVIDER
UART
WDT CLOCK
DIVIDER
WDT
WDTUEN
(WDT clock update enable)
watchdog oscillator
IRC oscillator
system oscillator
CLKOUT PIN CLOCK
DIVIDER
CLKOUT pin
CLKOUTUEN
(CLKOUT update enable)
002aae514
main clock
system clock
IRC oscillator
18