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Rev. 1.00
80 of 576
January 28, 2022
32-Bit Arm
®
Cortex
®
-M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253
6 Clock Control Unit (CKCU)
6
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), Low Speed
External crystal oscillator (LSE), Phase Lock Loop (PLL), HSE clock monitor, clock prescaler,
clock multiplexer and clock gating. The clocks of AHB, APB, and CPU are derived from system
clock (CK_SYS) which can come from HSI, HSE, LSI, LSE or PLL. Watchdog Timer and Real
Time Clock (RTC) use either LSI or LSE as their clock source. The maximum operating frequency
of system clock f
CK_AHB
can be up to 60 MHz.
A variety of internal clocks can also be wired out through CKOUT for debugging purpose. The
clock monitor can be used to get clock failure detection of HSE. Once the clock of HSE does not
function such as being broken down or removed, etc., CKCU will force to switch the system clock
source to the HSI clock to prevent system halt.