LPC2925 NXP Semiconductors, LPC2925 Datasheet - Page 42

• Manufacturer Part Number: LPC2925
• Description: (LPC2921 - LPC2925) ARM9 microcontroller
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2921_2923_2925_0
Preliminary data sheet
www.DataSheet4U.com
6.15.2.1 Functional description
6.15.2 Clock Generation Unit (CGU0)
The key features are:
Remark: Any clock-frequency adjustment has a direct impact on the timing of all on-board
peripherals.
The clock generation unit provides 11 internal clock sources as described in
Table 24.
[1]
[2]
For generation of these base clocks, the CGU consists of primary and secondary clock
generators and one output generator for each base clock.
Number Name
0
1
2
3
4
5
6
7
8
9
10
11
•
•
•
•
•
•
•
•
•
•
Generation of 11 base clocks selectable from several embedded clock sources.
Crystal oscillator with power-down.
Control PLL with power-down.
Very low-power ring oscillator, always on to provide a safe clock.
Seven fractional clock dividers with L/D division.
Individual source selector for each base clock, with glitch-free switching.
Autonomous clock-activity detection on every clock source.
Protection against switching to invalid or inactive clock sources.
Embedded frequency counter.
Register write-protection mechanism to prevent unintentional alteration of clocks.
Maximum frequency that guarantees stable operation of the LPC2921/2923/2925.
Fixed to low-power oscillator.
BASE_SAFE_CLK
BASE_SYS_CLK
BASE_PCR_CLK
BASE_IVNSS_CLK
BASE_MSCSS_CLK
BASE_ICLK0_CLK
BASE_UART_CLK
BASE_SPI_CLK
BASE_TMR_CLK
BASE_ADC_CLK
reserved
BASE_ICLK1_CLK
CGU0 base clocks
Rev. 00.01 — 24 October 2008
Frequency
(MHz)
0.4
100
0.4
100
100
160
100
50
100
4.5
-
160
[2]
[1]
ARM9 microcontroller with CAN and LIN
LPC2921/2923/2925
Description
base safe clock (always on)
base system clock
base PCR subsystem clock
base IVNSS subsystem clock
base MSCSS subsystem clock
base SPI clock
base timers clock
base ADCs clock
-
base internal clock 0, for CGU1
base UART clock
base internal clock 1, for CGU1
© NXP B.V. 2008. All rights reserved.
Table
24.
42 of 81