21.8.7 32.768 kHz External Crystal Oscillator (XOSC32K) Control


Bit	15	14	13	12	11	10	9	8
				WRTLOCK		STARTUP[2:0]
Access				R/W		R/W	R/W	R/W
Reset				0		0	0	0


Bit	7	6	5	4	3	2	1	0
	ONDEMAND	RUNSTDBY		EN1K	EN32K	XTALEN	ENABLE
Access	R/W	R/W		R/W	R/W	R/W	R/W
Reset	1	0		0	0	0	0

Bit 12 – WRTLOCK Write Lock

This bit locks the XOSC32K register for future writes, effectively freezing the XOSC32K configuration.

Value	Description
0	The XOSC32K configuration is not locked.
1	The XOSC32K configuration is locked.

Bits 10:8 – STARTUP[2:0] Oscillator Start-Up Time

This bit field selects the XOSC32K crystal oscillator stabilization time.

Important: This stabilization time is for guidance only. A major component of crystal start-up time is based on the second party crystal MFG parasitics that are outside the scope of this specification. If this is a major concern, the customer would need to characterize this based on their design choices.

Table 21-2. Stabilization Time for 32.768 kHz External Crystal Oscillator ⁽¹⁾
STARTUP[2:0]	Number of OSCULP32K Clock Cycles	Approximate Equivalent Time  ⁽²⁾[s]
0x0	2048	0.06
0x1	4096	0.13
0x2	16384	0.5
0x3	32768	1
0x4	65536	2
0x5	131072	4
0x6	262144	8
0x7	Reserved	Reserved

Note:

The OSCULP32K oscillator is used to clock the start-up counter.
Actual Start-Up time is the number of selected OSCULP32K cycles + 3 XOSC32K cycles.

Bit 7 – ONDEMAND On Demand Control

This bit controls how the XOSC32K behaves when a peripheral clock request is detected. For details, refer to XOSC32K Sleep Behavior.

Bit 6 – RUNSTDBY Run in Standby

This bit controls how the XOSC32K behaves during Standby sleep mode. For details, refer to XOSC32K Sleep Behavior.

Bit 4 – EN1K 1.024 kHz Output Enable

Value	Description
0	The 1.024 kHz output is disabled.
1	The 1.024 kHz output is enabled.

Bit 3 – EN32K 32.768 kHz Output Enable

Value	Description
0	The 32.768 kHz output is disabled.
1	The 32.768 kHz output is enabled.

Bit 2 – XTALEN Crystal Oscillator Enable

This bit controls the connections between the I/O pads and the external clock or crystal oscillator.

Value	Description
0	External clock connected on XIN32. XOUT32 can be used as general-purpose I/O.
1	Crystal connected to XIN32/XOUT32.

Bit 1 – ENABLE Oscillator Enable

Value	Description
0	The oscillator is disabled.
1	The oscillator is enabled.

Name:	XOSC32K
Offset:	0x14
Reset:	0x00000080
Property:	PAC Write-Protection