Product Specs

Table Of Contents
25 RTC Real-time counter
Page
244
Using the RTC TICK event rather than the SysTick allows the CPU to be powered down while still keeping
RTOS scheduling active.
Important: The TICK event is disabled by default.
25.6 Event control feature
To optimize RTC power consumption, events in the RTC can be individually disabled to prevent PCLK16M
and HFCLK being requested when those events are triggered. This is managed using the EVTEN register.
For example, if the TICK event is not required for an application, this event should be disabled as it is
frequently occurring and may increase power consumption if HFCLK otherwise could be powered down for
long durations.
This means that the RTC implements a slightly different task and event system compared to the standard
system described in Peripheral interface on page 68. The RTC task and event system is illustrated in Figure
46: Tasks, events and interrupts in the RTC on page 244.
Task signal from PPI
RTC
write
OR
task
RTC
core
event
IRQ signal to NVIC
m
INTEN
EVENT m
m
EVTEN
TASK
Event signal to PPI
Figure 46: Tasks, events and interrupts in the RTC
25.7 Compare feature
There are a number of Compare registers.
For more information, see Registers on page 248.
When setting a compare register, the following behavior of the RTC compare event should be noted:
If a CC register value is 0 when a CLEAR task is set, this will not trigger a COMPARE event.