ATMEGA406_0607 datasheet(49/263 Pages) ATMEL

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2548E–AVR–07/06

ATmega406

10. Wake-up Timer

The following section describes the Wake-up Timer in the ATmega406.

• One Wake-up Timer Interrupt

• 8 Selectable Time-out Periods

• Separate Wake-up Timer Calibration Flag

• Separate Clock Source

10.1

Overview

The Wake-up Timer is clocked either from the Slow RC Oscillator or from the external 32 kHz

crystal oscillator. See ”Run-Time Clock Source Select” on page 28 for details. By controlling the

Wake-up Timer prescaler, the Wake-up interval can be adjusted from 31.25 ms to 4 s. Eight dif-

ferent clock cycle periods can be selected to determine the Time-out period.

Figure 10-1. Wake-up Timer

10.2

10.2.1

WUTCSR – Wake-up Timer Control and Status Register

• Bit 7 – WUTIF: Wake-up Timer Interrupt Flag

The WUTIF bit is set (one) when an overflow occurs in the Wake-up Timer. WUTIF is cleared by

hardware when executing the corresponding interrupt handling vector. Alternatively, WUTIF is

cleared by writing a logic one to the flag. When the SREG I-bit, WUTIE (Wake-up Timer Interrupt

Enable), and WUTIF are set (one), the Wake-up Timer interrupt is executed.

SLOW RC

OSCILLATOR

WAKE-UP

WUTR

WUTP0

WUTP1

WUTP2

WUTE

WUTIF

WUTCF

32 kHz

OSCILLATOR

1/4

PRESCALER

clk

WUT

Bit

321

(0x62)

WUTIF

WUTIE

WUTCF

WUTR

WUTE

WUTP2

WUTP1

WUTP0

WUTCSR

Read/Write

R/W

Initial Value

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