STM8AL318X datasheet(19/131 Pages) STMICROELECTRONICS

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STM8AL318x STM8AL3L8x

Functional overview

Figure 2. Clock tree diagram

1. The HSE clock source is either an external crystal/ceramic resonator or an external source (HSE bypass).

Refer to Section HSE clock in STM8L051/L052 Value Line, STM8L151/L152, STM8L162, STM8AL31,

STM8AL3L MCU lines reference manual (RM0031).

2. The LSE clock source is either an external crystal/ceramic resonator or a external source (LSE bypass).

Refer to Section LSE clock in STM8L051/L052 Value Line, STM8L151/L152, STM8L162, STM8AL31,

STM8AL3L MCU lines reference manual (RM0031).

3.5

Low-power real-time clock

The real-time clock (RTC) is an independent binary coded decimal (BCD) timer/counter.

Six byte locations contain the second, minute, hour (12/24 hour), week day, date, month,

year, in BCD (binary coded decimal) format. Correction for 28, 29 (leap year), 30, and 31

day months are made automatically. The subsecond field is also readable in binary format.

The calendar is adjustable from 1 to 32767 RTC clock pulses. This allows to make a

synchronization to a master clock.

The RTC offers a digital calibration which allows an accuracy of +/-0.5ppm.

It provides a programmable alarm and programmable periodic interrupts with wakeup from

Halt capability.

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Periodic wakeup time using the 32.768 kHz LSE with the lowest resolution (of 61 µs) is

from min. 122 µs to max. 3.9 s. With a different resolution, the wakeup time reaches

36 hours

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Periodic alarms based on the calendar are generated from LSE period to every year

A clock security system detects a failure on LSE, and provides an interrupt with wakeup

capability. The RTC clock automatically switches to LSI in case of LSE failure.

The RTC also provides 3 anti-tamper detection pins. This detection embeds a

programmable filter and wakes-up the MCU.

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