lpc1778 NXP Semiconductors, lpc1778 Datasheet - Page 64

• Manufacturer Part Number: lpc1778
• Description: 32-bit Arm Cortex-m3 Microcontroller; Up To 512 Kb Flash And 96 Kb Sram; Usb Device/host/otg; Ethernet; Lcd; Emc
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC178x_7x
Objective data sheet
7.32.1.1 Internal RC oscillator
7.32.1.2 Main 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 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.
Fig 7.
system oscillator
IRC oscillator
LPC178x/7x clock generation block diagram
All information provided in this document is subject to legal disclaimers.
Rev. 00.04 — 8 July 2010
LPC178x/7x
alt_pll_clk
pll_clk
sysclk
sysclk
pll_clk
(system clock select)
(CPU clock select)
(USB clock select)
CLKSRCSEL
CCLKSEL
USBSEL
MAIN PLL0
ALT PLL1
32-bit ARM Cortex-M3 microcontroller
CLOCK DIVIDER
CLOCK DIVIDER
CLOCK DIVIDER
PERIPHERAL
PERIPHERAL
CPU CLOCK
DIVIDER
EMC
pll_clk
sysclk
alt_pll_clk
LPC178x/7x
© NXP B.V. 2010. All rights reserved.
cclk
pclk
emc_clk
usb_clk
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