Datasheet

157
Atmel | SMART SAM D20 [DATASHEET]
Atmel-42129K–SAM-D20_datasheet–06/2014
16.8.6 32kHz External Crystal Oscillator (XOSC32K) Control
Name: XOSC32K
Offset: 0x14
Reset: 0x0080
Property: Write-Protected
z Bits 15:13 – 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. These bits will always return zero when read.
z Bit 12 – WRTLOCK: Write Lock
This bit locks the XOSC32K register for futur writes to fix the XOSC32K configuration.
0: The XOSC32K configuration is not locked.
1: The XOSC32K configuration is locked.
z Bit 11 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
z Bits 10:8 – STARTUP[2:0]: Oscillator Start-Up Time
These bits select the start-up time for the oscillator according to Table 16-5
The OSCULP32K oscillator is used to clock the start-up counter.
Bit151413121110 9 8
WRTLOCK STARTUP[2:0]
Access R R R R/W R R/W R/W R/W
Reset00000000
Bit76543210
ONDEMAND RUNSTDBY AAMPEN EN1K EN32K XTALEN ENABLE
Access R/W R/W R/W R/W R/W R/W R/W R
Reset10000000
Table 16-5. Start-Up Time for 32kHz External Crystal Oscillator
STARTUP[2:0]
Number of OSCULP32K
Clock Cycles
(1)
Number of XOSC32K
Clock Cycles
(2)
Approximate Equivalent Time
(OSCULP = 32.768kHz)
(3)
0x0 1 3 122µs
0x1 32 3 1068µs
0x2 2048 3 62592µs
0x3 4096 3 125092µs
0x4 16384 3 500092µs
0x5 32768 3 1000092µs
0x6 65536 3 2000092µs
0x7 131072 3 4000092µs