UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
96 of 1269
NXP Semiconductors
UM10503
Chapter 11: LPC43xx Clock Generation Unit (CGU)
A similar two-step procedure applies when changing the BASE_M4_CLK from low to high
frequencies using the PLL0AUDIO as the clock source.
11.3 Features
•
PLL control
•
Supports three PLLs:
–
the PLL0USB for creating the 480 MHz clock for the high-speed USB0
–
the PLL0AUDIO with fractional divider for creating a wide variety of frequencies for
audio applications with high accuracy
–
the PLL1 for creating the core and peripheral clocks.
•
Oscillator control
•
Clock generation and clock source multiplexing
•
Integer dividers for clock output stages
11.4 General description
The CGU generates multiple independent clocks for the core and the peripheral blocks of
the LPC43x. Each independent clock is called a base clock and itself is one of the inputs
to the two Clock Control Units (CCUs) which control the branch clocks to the individual
peripherals (see
Fig 24. BASE_M4_CLK ramp-up procedure
12 MHz
90 MHz
110 MHz
204 MHz
BASE_M4_CLK
configure
crystal
oscillator
wake-up from
deep-sleep mode
power-down mode
crystal osc
PLL1
(crystal osc)
PLL1
(crystal osc)
IRC
BASE_M4_CLK clock source =
configure
PLL1 < 110 MHz
configure
PLL1 <= 204 MHz
100 μs