Datasheet

36
8116J–AVR–06/2013
XMEGA A3B
Not recommended for new designs -
Use ATxmega256A3BU
19. RTC32 - 32-bit Real-Time Counter
19.1 Features
• 32-bit resolution
• One 32-bit Compare register
• One 32-bit Period register
• Clear Timer on overflow
• Optional Interrupt/ Event on overflow and compare match
• Selectable clock reference
– 1.024 kHz
–1 Hz
• Isolated V
BAT
power domain with dynamic switch over from/to V
CC
power domain’
19.1.1 Overview
The 32-bit Real Time Counter (RTC) is a 32-bit counter, counting reference clock cycles and giv-
ing an event and/or an interrupt request when it reaches a configurable compare and/or top
value. The reference clock is generated from a high accuracy 32.768 kHz crystal, and the design
is optimized for low power consumption. The RTC typically operate in low power sleep modes,
keeping track of time and waking up the device at regular intervals.
The RTC input clock can be taken from a 1.024 kHz or 1 Hz prescaled output from the 32.768
kHz reference clock. The RTC will give a compare interrupt request and/or event when the coun-
ter value equals the Compare register value. The RTC will give an overflow interrupt request
and/or event when the counter value equals the Period register value. Counter overflow will also
reset the counter value to zero.
The 32-bit Real Time Counter (RTC) must be clocked from the 1 Hz output of a 32.768 kHz crys-
tal oscillator connected between the TOSC1 and TOSC2 pins when running from V
BAT
. For more
details on the 32-bit RTC refer to the “32-bit Real Time Counter” section in the XMEGA A
Manual.
Figure 19-1. Real Time Counter Overview
32-bit Period
=
32-bit Counter
32-bit Com pare
Overflow
1 Hz
1.024 kHz
Compare Match
=