Data Sheet

182
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
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. The listed maximum frequencies are recommendations, and might vary
based on capacitive load and crystal characteristics. Setting this bit group has no effect when the Automatic Ampli-
tude Gain Control is active.
Table 16-8. Oscillator Gain
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.
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
GAIN[2:0] Recommended Max Frequency
0x0 2MHz
0x1 4MHz
0x2 8MHz
0x3 16MHz
0x4 30MHz
0x5-0x7 Reserved
Table 16-7. Start-UpTime for External Multipurpose Crystal Oscillator (Continued)
STARTUP[3:0]
Number of
OSCULP32K Clock
Cycles
Number of XOSC
Clock Cycles
Approximate Equivalent Time
(1)(2)(3)