Datasheet

81
SAM9M10 [DATASHEET]
6355F–ATARM–12-Mar-13
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 generates 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 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
10
ALMIEN
rtt_int
RTT_MR
set
set
RTT_SR
read
RTT_SR
reset
reset
RTT_MR
reload
rtt_alarm
RTTRST
RTT_MR
RTTRST