NuMicro® NUC029LEE/NUC029SEE
32-bit Arm
®
Cortex
®
-M0 Microcontroller
Aug, 2018
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6.3 Clock Controller
6.3.1 Overview
The clock controller generates the clocks for the whole chip, including system clocks and all
peripheral clocks. The clock controller also implements the power control function with the
individually clock ON/OFF control, clock source selection and clock divider. The chip enters
Power-down mode when Cortex
®
-M0 core executes the WFI instruction only if the
PWR_DOWN_EN (PWRCON[7]) bit and PD_WAIT_CPU (PWRCON[8]) bit are both set to 1.
After that, chip enters Power-down mode and wait for wake-up interrupt source triggered to leave
Power-down mode. In the Power-down mode, the clock controller turns off the 4~24 MHz external
high speed crystal oscillator and 22.1184/48 MHz internal high speed RC oscillator to reduce the
overall system power consumption. The following figures show the clock generator and the
overview of the clock source control.
The clock generator consists of 6 clock sources as listed below:
32.768 kHz external low speed crystal oscillator (LXT)
4~24 MHz external high speed crystal oscillator (HXT)
Programmable PLL output clock frequency (PLL source can be selected from external
4~24 MHz external high speed crystal oscillator (HXT) or 22.1184 MHz internal high
speed RC oscillator (HIRC)) (PLL FOUT)
22.1184 MHz internal high speed RC oscillator (HIRC)
48 MHz internal high speed RC oscillator (HIRC48)
10 kHz internal low speed RC oscillator (LIRC)