STM8AL3LE8x datasheet(18/133 Pages) STMICROELECTRONICS

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Functional overview

STM8AL31E8x STM8AL3LE8x

18/133

DocID027180 Rev 5

3.3.3

Voltage regulator

The high-density STM8AL3xE8x devices embed an internal voltage regulator for generating

the 1.8 V power supply for the core and peripherals.

This regulator has two different modes:

•

Main voltage regulator mode (MVR) for Run, Wait for interrupt (WFI) and Wait for event

(WFE) modes.

•

Low-power voltage regulator mode (LPVR) for Halt, Active-halt, Low-power run and

Low-power wait modes.

When entering Halt or Active-halt modes, the system automatically switches from the MVR

to the LPVR in order to reduce current consumption.

3.4

Clock management

The clock controller distributes the system clock (SYSCLK) coming from different oscillators

to the core and the peripherals. It also manages clock gating for low-power modes and

ensures clock robustness.

Features

•

Clock prescaler: to get the best compromise between speed and current

consumption, the clock frequency to the CPU and peripherals has to be adjusted by a

programmable prescaler

•

Safe clock switching: Clock sources are adaptable safely on the fly in run mode

through a configuration register.

•

Clock management: To reduce power consumption, the clock controller stops the

clock to the core, individual peripherals or memory.

•

System clock sources: 4 different clock sources are available to drive the system

clock:

–

1-16 MHz High speed external crystal (HSE)

–

16 MHz High speed internal RC oscillator (HSI)

–

32.768 Low speed external crystal (LSE)

–

38 kHz Low speed internal RC (LSI)

•

RTC and LCD clock sources: the above four sources are available to clock the RTC

and the LCD, whatever the system clock.

•

Startup clock: After reset, the microcontroller restarts by default with an internal

2 MHz clock (HSI/8). The prescaler ratio and clock source is adjustable by the

application program as soon as the code execution starts.

•

Clock security system (CSS): This feature is enabled by software. If a HSE clock

failure occurs, the system clock is automatically switched to HSI.

•

Configurable main clock output (CCO): This outputs an external clock for use by the

application.

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