LPC1788FBD144 NXP Semiconductors, LPC1788FBD144 Datasheet - Page 61

• Manufacturer Part Number: LPC1788FBD144
• Description: The LPC1788 is a Cortex-M3 microcontroller for embedded applications featuring a high level of integration and low power consumption at frequencies of 120 MHz
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC178X_7X
Objective data sheet
7.33.1.1 Internal RC oscillator
7.33.1.2 Main oscillator
The IRC may be used 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 LPC178x/7x 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 alternate PLL1.
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
Fig 7.
main oscillator
IRC oscillator
LPC178x/7x clock generation block diagram
(osc_clk)
All information provided in this document is subject to legal disclaimers.
Section 7.33.2
Rev. 3 — 27 December 2011
LPC178x/7x
alt_pll_clk
pll_clk
sysclk
pll_clk
sysclk
(system clock select)
(CPU clock select)
(USB clock select)
for additional information.
CLKSRCSEL
USBCLKSEL
CCLKSEL
MAIN PLL0
ALT PLL1
32-bit ARM Cortex-M3 microcontroller
CLOCK DIVIDER
CLOCK DIVIDER
CLOCK DIVIDER
PERIPHERAL
CPU CLOCK
DIVIDER
EMC
USB
pll_clk
sysclk
alt_pll_clk
LPC178x/7x
© NXP B.V. 2011. All rights reserved.
cclk
pclk
emc_clk
usb_clk
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