Hse Clock Monitor; Clock Output Capability; Table 17. Ckout Clock Source - Holtek HT32F52342 User Manual

32-Bit Arm ® Cortex ® -M0+ MCU
HT32F52342/HT32F52352

HSE Clock Monitor

The HSE clock monitor function is enabled by the HSE Clock Monitor Enable bit CKMEN in the
Global Clock Control Register, GCCR. The HSE clock monitor function should be enabled after
the HSE oscillator start-up delay and disabled when the HSE oscillator is stopped. Once the HSE
oscillator failure is detected, the HSE oscillator will automatically be disabled. The HSE clock
stuck flag CKSF in the Global Clock Interrupt Register GCIR will be set and the HSE oscillator
failure event will be generated if the corresponding interrupt enable bit CKSIE in the GCIR is
set. This failure interrupt is connected to the CPU Non-Maskable Interrupt, NMI. When the HSE
oscillator failure occurs, the HSE will be turned off and the system clock will be switched to the
HSI automatically by the hardware. If the HSE is used as the clock input of the PLL circuit whose
output is used as the system clock, the PLL circuit will also be turned off as well as the HSE when
the failure happens.

Clock Output Capability

The device has the clock output capability to allow the clocks to be output on the specific external
output pin CKOUT. The configuration registers of the corresponding GPIO port must be well
configured in the Alternate Function I/O, AFIO, section to output the selected clock signal. There
are seven output clock signals to be selected via the device clock output source selection bits
CKOUTSRC in the Global Clock Configuration Register, GCFGR.

Table 17. CKOUT Clock Source

CKOUTSRC[2:0]
Rev. 1.30
000 CK_REF = CK_PLL / (CKREFPRE + 1) / 2
001 HCLKC / 16
010 CK_SYS / 16
011 CK_HSE / 16
100 CK_HSI / 16
101 CK_LSE
110 CK_LSI
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Clock Source
September 28, 2018