Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 253

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

The Real-time Timer is built around a 32-bit counter used to count roll-over events of the programmable 16-bit prescaler
which enables counting elapsed seconds from a 32 kHz slow clock source. It generates a periodic interrupt and/or
triggers an alarm on a programmed value.

It can be configured to be driven by the 1 Hz signal generated by the RTC, thus taking advantage of a calibrated 1 Hz
clock.

The slow clock source can be fully disabled to reduce power consumption when RTT is not required.



32-bit Free-running Counter on prescaled slow clock or RTC calibrated 1 Hz clock



16-bit Configurable Prescaler



Interrupt on Alarm

The Real-time Timer can be 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, 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

RTT_MR

RTTDIS

1

0

RTT_MR

CLKSRC

RTC1Hz