LPC1111 NXP [NXP Semiconductors], LPC1111 Datasheet - Page 25

• Manufacturer Part Number: LPC1111
• Description: 32-bit ARM Cortex-M0 microcontroller; up to 32 kB flash and 8 kB SRAM
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
LPC1111_12_13_14_1
Product data sheet
7.15.1.2 System oscillator
7.15.1.3 Watchdog oscillator
7.15.2 System PLL
7.15.3 Clock output
7.15.4 Wake-up process
7.15.5 Power control
Upon power-up or any chip reset, the LPC1111/12/13/14 use the IRC as the clock source.
Software may later switch to one of the other available clock sources.
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.
The watchdog oscillator can be used as a clock source that directly drives the CPU, the
watchdog timer, or the CLKOUT pin. The watchdog oscillator nominal frequency is
programmable between 7.8 kHz and 1.7 MHz. The frequency spread over processing and
temperature is ±40 %.
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
its frequency range while the PLL is providing the desired output frequency. The output
divider may be set to divide by 2, 4, 8, or 16 to produce the output clock. Since the
minimum output divider value is 2, it is insured that the PLL output has a 50 % duty cycle.
The PLL is turned off and bypassed following a chip reset and may be enabled by
software. The program must configure and activate the PLL, wait for the PLL to lock, and
then connect to the PLL as a clock source. The PLL settling time is 100 μs.
The LPC1111/12/13/14 features a clock output function that routes the IRC oscillator, the
system oscillator, the watchdog oscillator, or the main clock to an output pin.
The LPC1111/12/13/14 begin operation at power-up and when awakened from Deep
power-down mode by using the 12 MHz IRC oscillator as the clock source. This allows
chip operation to resume quickly. If the system oscillator or the PLL is needed by the
application, software will need to enable these features and wait for them to stabilize
before they are used as a clock source.
The LPC1111/12/13/14 support a variety of power control features. There are three
special modes of processor power reduction: Sleep mode, Deep-sleep mode, and Deep
power-down mode. The CPU clock rate may also be controlled as needed by changing
clock sources, reconfiguring PLL values, and/or altering the CPU clock divider value. This
allows a trade-off of power versus processing speed based on application requirements.
In addition, a register is provided for shutting down the clocks to individual on-chip
peripherals, allowing fine tuning of power consumption by eliminating all dynamic power
use in any peripherals that are not required for the application. Selected peripherals have
their own clock divider which provides even better power control.
All information provided in this document is subject to legal disclaimers.
Rev. 01 — 16 April 2010
32-bit ARM Cortex-M0 microcontroller
LPC1111/12/13/14
© NXP B.V. 2010. All rights reserved.
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