
91
XMEGA A [MANUAL]
8077I–AVR–11/2012
Bit 2 – RC32KRDY: 32.768kHz Internal Oscillator Ready
This flag is set when the 32.768kHz internal oscillator is stable and is ready to be used as the system clock source.
Bit 1 – RC32MRDY: 32MHz Internal Oscillator Ready
This flag is set when the 32MHz internal oscillator is stable and is ready to be used as the system clock source.
Bit 0 – RC2MRDY: 2MHz Internal Oscillator Ready
This flag is set when the 2MHz internal oscillator is stable and is ready to be used as the system clock source.
7.10.3
XOSCCTRL – XOSC Control register
Bit 7:6 – FRQRANGE[1:0]: 0.4 - 16MHz Crystal Oscillator Frequency Range Select
These bits select the frequency range for the connected crystal oscillator according to
Table 7-5.
Table 7-5.
16MHz crystal oscillator frequency range selection.
Note:
Refer to Electrical characteristics section in device datasheet to retrieve the best setting for a given frequency.
Bit 5 – X32KLPM: Crystal Oscillator 32.768kHz Low Power Mode
Setting this bit enables the low power mode for the 32.768kHz crystal oscillator. This will reduce the swing on the TOSC2
pin.
Bit 4 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to zero
when this register is written.
Bit 3:0 – XOSCSEL[3:0]: Crystal Oscillator Selection
These bits select the type and start-up time for the crystal or resonator that is connected to the XTAL or TOSC pins. See
Table 7-6 on page 91 for crystal selections. If an external clock or external oscillator is selected as the source for the
Table 7-6.
External oscillator selection and start-up time.
Bit
7
6
5
4
321
0
+0x02
FRQRANGE[1:0]
X32KLPM
-XOSCSEL[3:0]
Read/Write
R/W
R
R/W
Initial Value
0
FRQRANGE[1:0]
Group
Configuration
Typical
Frequency Range
Recommended Range for Capacitors C1 and C2 (pF)
00
04TO2
0.4MHz - 2MHz
100
01
2TO9
2MHz - 9MHz
15
10
9TO12
9MHz - 12MHz
15
11
12TO16
12MHz - 16MHz
10
XOSCSEL[3:0]
Group Configuration
Selected Clock Source
Start-up Time
0000
External Clock
6 CLK
0010
32.768kHz TOSC
16K CLK