Holtek HT32F50231 User Manual page 80

32-Bit Arm ® Cortex ® -M0+ MCU
HT32F50231/HT32F50241
Bits Field
[8] HSEGAIN
[2:0] SW
Rev. 1.00
Descriptions
External High Speed Clock Gain Selection
0: HSE low gain mode
1: HSE high gain mode
System Clock Switch
010: CK_HSE as system clock
011: CK_HSI as system clock
110: CK_LSE as system clock
111: CK_LSI as system clock
Others: CK_HSI as system clock
These bits are set and reset by software to select CK_SYS source. If the HSE
oscillator is used directly or indirectly as the system clock and the HSE clock monitor
function is enabled, once the HSE failure is detected, these bits will be set by
hardware to force HSI (b011) as the system clock.
Note: When switch the system clock using the SW bits, the system clock is not
immediately switched and a certain delay is necessary. The software can
monitor the CKSWST bit in the clock source status register CKSTR to make
sure which clock is currently used as system clock.
80 of 486 July 31, 2018