STM8AF5178 datasheet(19/110 Pages) STMICROELECTRONICS

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STM8AF52/62xx, STM8AF51/61xx

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Doc ID 14395 Rev 9

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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

I2C

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