Clock Control Unit (Ckcu); Introduction - Holtek HT32F52220 User Manual

32-Bit Arm ® Cortex ® -M0+ MCU
HT32F52220/HT32F52230
6

Clock Control Unit (CKCU)

Introduction

The Clock Control unit (CKCU) provides functions of high speed internal RC oscillator (HSI),
High speed external crystal oscillator (HSE), Low speed internal RC oscillator (LSI), Phase Lock
Loop (PLL), HSE clock monitor, clock prescaler, clock multiplexer and clock gating. The clock of
AHB, APB, and CPU are derived from system clock (CK_SYS) which can come from HSI, HSE,
LSI or PLL. The Watchdog Timer uses the LSI as the clock source.
A variety of internal clocks can also be wired out through the CKOUT pin for debugging purpose.
The clock monitor can be used to detect the HSE clock failure. Once the HSE clock does not
normally function, which could be broken down or removed, etc., the CKCU will force to switch
the system clock source to the HSI clock to prevent system halt.
Rev. 1.10 69 of 366 November 09, 2018