LPC2921_23_25 NXP Semiconductors, LPC2921_23_25 Datasheet - Page 43

• Manufacturer Part Number: LPC2921_23_25
• Description: The LPC2921/2923/2925 combine an ARM968E-S CPU core with two integrated TCMblocks operating at frequencies of up to 125 MHz, Full-speed USB 2
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2921_23_25_3
Product data sheet
Fig 9.
CLOCK GENERATION UNIT (CGU0)
400 kHz LP_OSC
Block diagram of the CGU0 (see
OSCILLATOR
EXTERNAL
FREQUENCY
MONITOR
There are two primary clock generators: a low-power ring oscillator (LP_OSC) and a
crystal oscillator. See
LP_OSC is the source for the BASE_PCR_CLK that clocks the CGU itself and for
BASE_SAFE_CLK that clocks a minimum of other logic in the device (like the watchdog
timer). To prevent the device from losing its clock source LP_OSC cannot be put into
power-down. The crystal oscillator can be used as source for high-frequency clocks or as
an external clock input if a crystal is not connected.
Secondary clock generators are a PLL and seven fractional dividers (FDIV[0:6]). The PLL
has three clock outputs: normal, 120° phase-shifted and 240° phase-shifted.
PLL
clkout
clkout120
clkout240
DETECTION
CLOCK
All information provided in this document is subject to legal disclaimers.
Table 24
Figure
Rev. 03 — 14 April 2010
AHB TO DTL BRIDGE
for all base clocks)
9.
FDIV0
FDIV1
FDIV6
ARM9 microcontroller with CAN, LIN, and USB
LPC2921/2923/2925
OUT 0
OUT 1
OUT 2
OUT 3
OUT 11
002aae147
© NXP B.V. 2010. All rights reserved.
BASE_SAFE_CLK
BASE_SYS_CLK
BASE_PCR_CLK
BASE_IVNSS_CLK
BASE_ICLK1_CLK
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