AT91SAM9G45-CU datasheet(85/1159 Pages) ATMEL

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6438D–ATARM–13-Oct-09

AT91SAM9G45

13. Real-time Timer (RTT)

13.1

Description

The Real-time Timer is built around a 32-bit counter and used to count elapsed seconds. It gen-

erates a periodic interrupt and/or triggers an alarm on a programmed value.

13.2

Embedded Characteristics

• Real-Time Timer, allowing backup of time with different accuracies

– 32-bit Free-running back-up Counter

– Integrates a 16-bit programmable prescaler running on slow clock

– Alarm Register capable to generate a wake-up of the system through the Shut Down

Controller

13.3

Block Diagram

Figure 13-1. Real-time Timer

13.4

Functional Description

The Real-time Timer is used to count elapsed seconds. It is built around a 32-bit counter fed by

Slow Clock divided by a programmable 16-bit value. The value can be programmed in the field

RTPRES of the Real-time Mode Register (RTT_MR).

Programming RTPRES at 0x00008000 corresponds to feeding the real-time counter with a 1 Hz

signal (if the Slow Clock is 32.768 kHz). The 32-bit counter can count up to 2

32 seconds, corre-

sponding to more than 136 years, then roll over to 0.

SLCK

RTPRES

RTTINC

ALMS

16-bit

Divider

32-bit

Counter

ALMV

CRTV

RTT_MR

RTT_VR

RTT_AR

RTT_SR

RTTINCIEN

RTT_MR

ALMIEN

rtt_int

RTT_MR

set

RTT_SR

read

RTT_SR

reset

RTT_MR

reload

rtt_alarm

RTTRST

RTT_MR

RTTRST

AT91SAM9G45-CU Datasheet(PDF) 85 Page - ATMEL Corporation

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