Datasheet

LPC1102_1104 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 7 — 26 September 2013 14 of 43
NXP Semiconductors
LPC1102/1104
32-bit ARM Cortex-M0 microcontroller
7.14.1.1 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 LPC1102/1104 use the IRC as the clock source.
Software may later switch to one of the other available clock sources.
7.14.1.2 Watchdog oscillator
The watchdog oscillator can be used as a clock source that directly drives the CPU or the
watchdog timer. The watchdog oscillator nominal frequency is programmable between
9.4 kHz to 2.3 MHz. The frequency spread over processing and temperature is 40 %.
7.14.2 System PLL
The PLL accepts an input clock frequency in the range of 10 MHz to 25 MHz. The input
frequency is multiplied up to a high frequency with a Current Controlled Oscillator (CCO).
The multiplier can be an integer value from 1 to 32. The CCO operates in the range of
156 MHz to 320 MHz, so there is an additional divider in the loop to keep the CCO within
Fig 4. LPC1102/1104 clock generation block diagram
SYSTEM PLL
IRC oscillator
external clock
watchdog oscillator
IRC oscillator
watchdog oscillator
MAINCLKSEL
(main clock select)
SYSPLLCLKSEL
(system PLL clock select)
SYSTEM CLOCK
DIVIDER
AHB clock 0
(system)
AHBCLKCTRL[1:18]
(AHB clock enable)
AHB clocks 1 to 18
(memories
and peripherals)
SPI0 PERIPHERAL
CLOCK DIVIDER
SPI0
UART PERIPHERAL
CLOCK DIVIDER
UART
WDT CLOCK
DIVIDER
WDT
WDTUEN
(WDT clock update enable)
002aaf527
main clock
system clock
IRC oscillator
18
watchdog oscillator
IRC oscillator
system oscillator
CLKOUT PIN CLOCK
DIVIDER
CLKOUT pin
CLKOUTUEN
(CLKOUT update enable)