17.8.7 32kHz Internal Oscillator (OSC32K) Control

Name:	OSC32K
Offset:	0x18
Reset:	0x003F0080
Property:	Write-Protected


Bit	31	30	29	28	27	26	25	24

Access
Reset


Bit	23	22	21	20	19	18	17	16
		CALIB[6:0]
Access		R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset		0	1	1	1	1	1	1


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				EN32K	ENABLE
Access	R/W	R/W				R/W	R/W
Reset	1	0				0	0

Bits 22:16 – CALIB[6:0] Oscillator Calibration

These bits control the oscillator calibration.

This value must be written by the user.

Factory calibration values can be loaded from the non-volatile memory.

Bit 12 – WRTLOCK Write Lock

This bit locks the OSC32K register for future writes to fix the OSC32K configuration.

Value	Description
0	The OSC32K configuration is not locked.
1	The OSC32K configuration is locked.

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

These bits select start-up time for the oscillator.

The OSCULP32K oscillator is used as input clock to the startup counter.

Table 17-7. Start-Up Time for 32kHz Internal Oscillator
STARTUP[2:0]	Number of OSC32K clock cycles	Approximate Equivalent Time (OSCULP= 32 kHz)⁽¹⁾⁽²⁾⁽³⁾
0x0	3	92μs
0x1	4	122μs
0x2	6	183μs
0x3	10	305μs
0x4	18	549μs
0x5	34	1038μs
0x6	66	2014μs
0x7	130	3967μs

Notes: 1. Number of cycles for the start-up counter.

2. Number of cycles for the synchronization delay, before PCLKSR.OSC32KRDY is set.

3. Start-up time is n OSC32K cycles + 2 OSC32K cycles.

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, that is, if the ONDEMAND bit has been previously written to one, the oscillator will only be running 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 OSC32K.RUNSTDBY bit is one. If OSC32K.RUNSTDBY is zero, the oscillator is disabled.

Value	Description
0	The oscillator is always on, if enabled.
1	The oscillator is enabled when a peripheral is requesting the oscillator to be used as a clock source. The oscillator is disabled if no peripheral is requesting the clock source.

Bit 6 – RUNSTDBY Run in Standby

This bit controls how the OSC32K behaves during Standby Sleep mode:

Value	Description
0	The oscillator is disabled in standby sleep mode.
1	The oscillator is not stopped in standby sleep mode. If OSC32K.ONDEMAND is one, the clock source will be running when a peripheral is requesting the clock. If OSC32K.ONDEMAND is zero, the clock source will always be running in standby sleep mode.