Datasheet

87
SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
12. Real-time Timer (RTT)
12.1 Description
The Real-time Timer (RTT) 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.
12.2 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 Shutdown Controller
12.3 Block Diagram
Figure 12-1. Real-time Timer
12.4 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, 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
10
ALMIEN
rtt_int
RTT_MR
set
set
RTT_SR
read
RTT_SR
reset
reset
RTT_MR
reload
rtt_alarm
RTTRST
RTT_MR
RTTRST