93
XMEGA B [DATASHEET]
8291B–AVR–01/2013
Bit 2:1 – RC32MCREF[1:0]: 32MHz Oscillator Calibration Reference
These bits are used to select the calibration source for the 32MHz DFLL according to the
select only which calibration source to use for the DFLL. In addition, the actual clock source that is selected must enabled
and configured for the calibration to function.
Table 7-10. 32MHz oscillator reference design.
Bit 0 – RC2MCREF: 2MHz Oscillator Calibration Reference
This bit is used to select the calibration source for the 2MHz DFLL. By default, this bit is zero and the 32.768kHz internal
oscillator is selected. If this bit is set to one, the 32.768kHz crystal oscillator on TOSC is selected as the reference. This
bit will select only which calibration source to use for the DFLL. In addition, the actual clock source that is selected must
enabled and configured for the calibration to function.
7.11
Register Description
–
DFLL32M/DFLL2M
7.11.1 CTRL – Control register
Bit 7:1 – 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 0 – ENABLE: Enable
Setting this bit enables the DFLL and auto-calibration of the internal oscillator. The reference clock must be enabled and
stable before the DFLL is enabled.
After disabling the DFLL, the reference clock can not be disabled before the ENABLE bit is read as zero.
7.11.2 CALA – Calibration register A
The CALA and CALB registers hold the 13-bit DFLL calibration value that is used for automatic run-time calibration of the
internal oscillator. When the DFLL is disabled, the calibration registers can be written by software for manual run-time
calibration of the oscillator. The oscillators will also be calibrated according to the calibration value in these registers
when the DFLL is disabled.
RC32MCREF[1:0]
Group Configuration
Description
00
RC32K
32.768kHz internal oscillator
01
XOSC32
32.768kHz crystal oscillator on TOSC
10
USBSOF
USB start of frame
11
—
Reserved
Bit
7
6
5
4
3
2
1
0
–
–
–
–
–
–
–
ENABLE
Read/Write
R
R
R
R
R
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
–
CALA[6:0]
Read/Write
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
x
x
x
x
x
x
x
Summary of Contents for XMEGA B
Page 320: ...320 XMEGA B DATASHEET 8291B AVR 01 2013 Table 25 12 7 segments Character Table...
Page 321: ...321 XMEGA B DATASHEET 8291B AVR 01 2013 Table 25 13 14 segments Character Table...
Page 322: ...322 XMEGA B DATASHEET 8291B AVR 01 2013 Table 25 14 16 segments Character Table...
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