- NXP ARM Microcontroller Product Data Sheet

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LPC2917_19_1 © NXP B.V. 2007. All rights reserved.
Preliminary data sheet Rev. 1.01 — 15 November 2007 42 of 68
NXP Semiconductors
LPC2917/19
ARM9 microcontroller with CAN and LIN
• 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
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.
8.8.4.2 Description
The clock generation unit provides 10 internal clock sources as described in Table 23
.
[1] Maximum frequency that guarantees stable operation of the LPC2917/19.
[2] Fixed to low-power oscillator.
For generation of these base clocks, the CGU consists of primary and secondary clock
generators and one output generator for each base clock.
Table 23. CGU base clocks
Number Name Frequency
(MHz)
[1]
Description
0 BASE_SAFE_CLK 0.4 Base safe clock (always on)
1 BASE_SYS_CLK 80 Base system clock
2 BASE_PCR_CLK 0.4
[2]
Base PCR subsystem clock
3 BASE_IVNSS_CLK 80 Base IVNSS subsystem clock
4 BASE_MSCSS_CLK 80 Base MSCSS subsystem clock
5 BASE_UART_CLK 80 Base UART clock
6 BASE_SPI_CLK 40 Base SPI clock
7 BASE_TMR_CLK 80 Base timers clock
8 BASE_ADC_CLK 4.5 Base ADCs clock