STM8S datasheet(114/467 Pages) STMICROELECTRONICS

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Auto-wakeup (AWU)

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Auto-wakeup (AWU)

12.1

AWU introduction

The AWU is used to provide an internal wakeup time base that is used when the MCU goes

into Active-halt power saving mode. This time base is clocked by the low speed internal

(LSI) RC oscillator clock or the HSE crystal oscillator clock divided by a prescaler.

12.2

LSI clock measurement

To ensure the best possible accuracy when using the LSI clock, its frequency can be

measured with TIM3 or TIM1 timer input capture 1 (see datasheet for information on which

timer is connected in the specific product).

Figure 25. AWU block diagram

1. The LS clock source is selected by programming the CKAWUSEL option bit as explained in the clock

controller chapter.

MSv45269V1

6-BIT PROG

COUNTER

AWU COUNTERS

HSE clock

(1 – 24 MHz)

PRSC [1:0]

OPTION bits

CKAWUSEL

OPTION bit

~ 128 kHz LS clock

MSR

To timer input capture

(for measurement)

fLS

APR[5:0]

AWUTB [3:0]

15 time bases

AWUEN & HALT/WAIT

AWU interrupt

Prescaler

LSI RC

128 kHz

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