16.6.3.1 32-Bit Counter (Mode 0)
When the RTC Operating Mode bits in the Control register are zero
(CTRL.MODE=00
), the counter operates in 32-bit Counter mode. The block
diagram of this mode is shown in Figure 16-1. When the RTC is enabled, the counter will increment on
every 0-to-1 transition of CLK_RTC_CNT. The counter will increment until it reaches the top
value of 0xFFFFFFFF, and then wrap to 0x00000000. This sets the Overflow Interrupt flag in
the Interrupt Flag Status and Clear register (INTFLAG.OVF).
The RTC counter value can be read from or written to the Counter Value register (COUNT) in 32-bit format.
The counter value is continuously compared with the 32-bit Compare register (COMP). When a compare match occurs, the Compare Interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.CMP) is set on the next 0-to-1 transition of CLK_RTC_CNT.
If the Clear on Match bit in the Control
register (CTRL.MATCHCLR) is '1
', the counter is cleared on the next
counter cycle when a compare match with COMP occurs. This
allows the RTC to generate periodic interrupts or events with longer periods than are
possible with the prescaler events. Note that when CTRL.MATCHCLR is '1
',
INTFLAG.CMP and INTFLAG.OVF will both be set
simultaneously on a compare match with COMP.