Datasheet

STM8AF52/62xx, STM8AF51/61xx Product overview
Doc ID 14395 Rev 9 19/110
5.5.3 128 kHz low-speed internal RC oscillator (LSI)
The frequency of this clock is 128 kHz and it is independent from the main clock. It drives
the independent watchdog or the AWU wakeup timer.
In systems which do not need independent clock sources for the watchdog counters, the
128 kHz signal can be used as the system clock. This configuration has to be enabled by
setting an option byte (OPT3/OPT3N, bit LSI_EN).
5.5.4 24 MHz high-speed external crystal oscillator (HSE)
The external high-speed crystal oscillator can be selected to deliver the main clock in
normal Run mode. It operates with quartz crystals and ceramic resonators.
● Frequency range: 1 MHz to 24 MHz
● Crystal oscillation mode: preferred fundamental
● I/Os: standard I/O pins multiplexed with OSCIN, OSCOUT
5.5.5 External clock input
An external clock signal can be applied to the OSCIN input pin of the crystal oscillator. The
frequency range is 0 to 24 MHz.
5.5.6 Clock security system (CSS)
The clock security system protects against a system stall in case of an external crystal clock
failure.
In case of a clock failure an interrupt is generated and the high-speed internal clock (HSI) is
automatically selected with a frequency of 2 MHz (16 MHz/8).
Table 6. Peripheral clock gating bits (CLK_PCKENR1)
Control bit Peripheral
PCKEN17 TIM1
PCKEN16 TIM3
PCKEN15 TIM2
PCKEN14 TIM4
PCKEN13 LINUART
PCKEN12 USART
PCKEN11 SPI
PCKEN10 I
2
C