lpc2917 NXP Semiconductors, lpc2917 Datasheet - Page 42

• Manufacturer Part Number: lpc2917
• Description: Arm9 Microcontroller With Can And Lin
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2917_19_1
Preliminary data sheet
8.8.4.2 Description
Remark: Any clock-frequency adjustment has a direct impact on the timing of on-board
peripherals such as the UARTs, SPI, watchdog, timers, CAN controller, LIN master
controller, ADCs or flash-memory interface.
The clock generation unit provides 10 internal clock sources as described in
Table 23.
[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
•
•
•
•
•
•
•
•
•
•
Generation of 10 and 2 test-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 LPC2917/19.
Fixed to low-power oscillator.
BASE_SAFE_CLK
BASE_SYS_CLK
BASE_PCR_CLK
BASE_IVNSS_CLK
BASE_MSCSS_CLK
BASE_UART_CLK
BASE_SPI_CLK
BASE_TMR_CLK
BASE_ADC_CLK
CGU base clocks
Rev. 1.01 — 15 November 2007
Frequency
(MHz)
0.4
80
0.4
80
80
80
40
80
4.5
[2]
[1]
ARM9 microcontroller with CAN and LIN
Description
Base safe clock (always on)
Base system clock
Base PCR subsystem clock
Base IVNSS subsystem clock
Base MSCSS subsystem clock
Base UART clock
Base SPI clock
Base timers clock
Base ADCs clock
LPC2917/19
© NXP B.V. 2007. All rights reserved.
Table
23.
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