224
8331B–AVR–03/12
Atmel AVR XMEGA AU
• Bit 7:0
–
CNT[7:0]: Counter Value Low
These bits hold the LSB of the 16-bit real-time counter value.
18.3.7
CNTH – Counter Register High
• Bit 7:0 – CNT[15:8]: Counter Value High
These bits hold the MSB of the 16-bit real-time counter value.
18.3.8
PERL – Period Register Low
The PERH and PERL register pair represents the 16-bit value, PER. PER is constantly com-
pared with the counter value (CNT). A match will set OVFIF in the INTFLAGS register and clear
CNT. Reading and writing 16-bit values requires special attention. Refer to
for details.
Due to synchronization between the RTC clock and system clock domains, there is a latency of
two RTC clock cycles from updating the register until this has an effect. Application software
needs to check that the SYNCBUSY flag in the
”STATUS – Status register” on page 222
is
cleared before writing to this register.
• Bit 7:0 – PER[7:0]: Period Low
These bits hold the LSB of the 16-bit RTC TOP value.
18.3.9
PERH – Period Register High
• Bits 7:0 – PER[15:8]: Period High
These bits hold the MSB of the 16-bit RTC TOP value.
Bit
7
6
5
4
3
2
1
0
CNT[15:8]
CNTH
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
PER[7:0]
PERL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
1
1
1
1
1
1
1
1
Bit
7
6
5
4
3
2
1
0
PER[15:8]
PERH
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
1
1
1
1
1
1
1
1