LPC1767 NXP [NXP Semiconductors], LPC1767 Datasheet - Page 31

• Manufacturer Part Number: LPC1767
• Description: 32-bit ARM Cortex-M3 microcontroller; up to 512 kB flash and 64 kB SRAM with Ethernet, USB 2.0 Host/Device/OTG, CAN
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
LPC1769_68_67_66_65_64_4
Product data sheet
Fig 4.
LPC17xx clocking generation block diagram
7.29.1.1 Internal RC oscillator
7.29.1.2 Main oscillator
7.29.1.3 RTC oscillator
LPC17xx
OSCILLATOR
OSCILLATOR
OSCILLATOR
INTERNAL
MAIN
RTC
RC
See
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 4 MHz. The IRC is
trimmed to 1 % accuracy over the entire voltage and temperature range.
Upon power-up or any chip reset, the LPC17xx use the IRC as the clock source. Software
may later switch to one of the other available clock sources.
The main oscillator can be used as the clock source for the CPU, with or without using the
PLL. The main oscillator also provides the clock source for the dedicated USB PLL.
The main 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 main
PLL. The clock selected as the PLL input is PLLCLKIN. The ARM processor clock
frequency is referred to as CCLK elsewhere in this document. The frequencies of
PLLCLKIN and CCLK are the same value unless the PLL is active and connected. The
clock frequency for each peripheral can be selected individually and is referred to as
PCLK. Refer to
The RTC oscillator can be used as the clock source for the RTC block, the main PLL,
and/or the CPU.
32 kHz
Figure 4
(CLKSRCSEL)
system
select
rtclk = 1Hz
clock
for an overview of the LPC17xx clock generation.
pclk
Section 7.29.2
WDT
WATCHDOG
MAIN PLL
USB PLL
TIMER
Rev. 04 — 1 February 2010
REAL-TIME
CLOCK
main PLL enable
for additional information.
pllclk
LPC1769/68/67/66/65/64
PERIPHERAL
GENERATOR
CLOCK
CPU clock config
USB clock config
(USBCLKCFG)
(CCLKCFG)
DIVIDER
DIVIDER
CLOCK
CLOCK
CPU
USB
32-bit ARM Cortex-M3 microcontroller
CCLK/4
CCLK/2
CCLK
CCLK/8
CCLK/6
cclk
USB PLL enable
CORTEX-M3
(48 MHz)
ETHERNET
usbclk
BLOCK
ARM
GPIO
NVIC
DMA
USB BLOCK
APB peripherals
© NXP B.V. 2010. All rights reserved.
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