Atmel Evaluation Kit AT91SAM9M10-G45-EK AT91SAM9M10-G45-EK Data Sheet

 81

SAM9M10 [DATASHEET]

6355F–ATARM–12-Mar-13

The Real-time Timer is built around a 32-bit counter and used to count elapsed seconds. It generates a periodic
interrupt and/or triggers an alarm on a programmed value.

• 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

Real-time Timer 

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 Regis-
ter (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, corresponding 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

0

1

0

ALMIEN

rtt_int

RTT_MR

set

set

RTT_SR

read

RTT_SR 

reset

reset

RTT_MR

reload

rtt_alarm 

RTTRST

RTT_MR

RTTRST