Datasheet
19.5.1 I/O Lines
Not applicable.
19.5.2 Power Management
The RTC will continue to operate in any sleep mode where the selected source clock is running. The RTC
interrupts can be used to wake up the device from sleep modes. Events connected to the event system
can trigger other operations in the system without exiting sleep modes. Refer to the Power Manager for
details on the different sleep modes.
The RTC will be reset only at power-on (POR) or by setting the Software Reset bit in the Control register
(CTRL.SWRST=1).
Related Links
16. PM – Power Manager
19.5.3 Clocks
The RTC bus clock (CLK_RTC_APB) can be enabled and disabled in the Power Manager, and the
default state of CLK_RTC_APB can be found in the Peripheral Clock Masking section.
A generic clock (GCLK_RTC) is required to clock the RTC. This clock must be configured and enabled in
the Generic Clock Controller before using the RTC. Refer to GCLK – Generic Clock Controller for details.
This generic clock is asynchronous to the user interface clock (CLK_RTC_APB). Due to this
asynchronicity, accessing certain registers will require synchronization between the clock domains. Refer
to 19.6.8 Synchronization for further details.
The RTC should not work with the Generic Clock Generator 0.
Related Links
16.6.2.6 Peripheral Clock Masking
15. GCLK - Generic Clock Controller
19.5.4 DMA
Not applicable.
19.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the RTC interrupts requires the
Interrupt Controller to be configured first. Refer to Nested Vector Interrupt Controller for details.
Related Links
11.2 Nested Vector Interrupt Controller
19.5.6 Events
The events are connected to the Event System.
Related Links
24. EVSYS – Event System
19.5.7 Debug Operation
When the CPU is halted in debug mode the RTC will halt normal operation. The RTC can be forced to
continue operation during debugging. Refer to the Debug Control (DBGCTRL) register for details.
SAM D21 Family
RTC – Real-Time Counter
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 258