Atmel Xplained Pro Evaluation Kit ATSAMD20-XPRO ATSAMD20-XPRO Data Sheet

155

Atmel | SMART SAM D20 [DATASHEET]

Atmel-42129K–SAM-D20_datasheet–06/2014

Notes:

1.

Number of cycles for the start-up counter.

2.

Number of cycles for the synchronization delay, before PCLKSR.XOSCRDY is set.

3.

Actual start-up time is n OSCULP32K cycles + 3 XOSC cycles, but given the time neglects the 3 XOSC cycles.

z

Bit 11 – AMPGC: Automatic Amplitude Gain Control
0: The automatic amplitude gain control is disabled.

1: The automatic amplitude gain control is enabled. Amplitude gain will be automatically adjusted during Crystal 
Oscillator operation.

z

Bits 10:8 – GAIN[2:0]: Oscillator Gain
These bits select the gain for the oscillator, given in table 

. The listed maximum frequencies are recom-

mendations, and might vary based on capacitive load and crystal characteristics. Setting this bit group has no 
effect when the Automatic Amplitude Gain Control is active.

z

Bit 7 – ONDEMAND: On Demand Control
The On Demand operation mode allows an oscillator to be enabled or disabled, depending on peripheral clock 
requests. 

In On Demand operation mode, i.e., if the XOSC.ONDEMAND bit has been previously written to one, the oscillator 
will be running only when requested by a peripheral. If there is no peripheral requesting the oscillator’s clock 
source, the oscillator will be in a disabled state. 

If On Demand is disabled, the oscillator will always be running when enabled.

In standby sleep mode, the On Demand operation is still active if the XOSC.RUNSTDBY bit is one. If 
XOSC.RUNSTDBY is zero, the oscillator is disabled.

0x6

64

3

1953µs

0x7

128

3

3906µs

0x8

256

3

7813µs

0x9

512

3

15625µs

0xA

1024

3

31250µs

0xB

2048

3

62500µs

0xC

4096

3

125000µs

0xD

8192

3

250000µs

0xE

16384

3

500000µs

0xF

32768

3

1000000µs

0x0

2MHz

0x1

4MHz

0x2

8MHz

0x3

16MHz

0x4

30MHz

0x5-0x7

Reserved