16.8.7 32kHz Internal Oscillator (OSC32K) Control

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

Bit 3130292827262524 
          
Access  
Reset  
Bit 2322212019181716 
  CALIB[6:0] 
Access R/WR/WR/WR/WR/WR/WR/W 
Reset 0111111 
Bit 15141312111098 
    WRTLOCK STARTUP[2:0] 
Access R/WR/WR/WR/W 
Reset 0000 
Bit 76543210 
 ONDEMANDRUNSTDBY   EN32KENABLE  
Access R/WR/WR/WR/W 
Reset 1000 

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.

ValueDescription
0The OSC32K configuration is not locked.
1The 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 16-4. Start-Up Time for 32kHz Internal Oscillator
STARTUP[2:0] Number of OSC32K clock cyclesApproximate Equivalent Time

(OSCULP= 32 kHz)(1)(2)(3)

0x0392μs
0x14122μs
0x26183μs
0x310305μs
0x418549μs
0x5341038μs
0x6662014μs
0x71303967μs

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, i.e., 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.

ValueDescription
0The oscillator is always on, if enabled.
1The 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:

ValueDescription
0The oscillator is disabled in standby sleep mode.
1The 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.

Bit 2 – EN32K 32kHz Output Enable

ValueDescription
0The 32kHz output is disabled.
1The 32kHz output is enabled.
0The oscillator is disabled.
1The oscillator is enabled.

Bit 1 – ENABLE Oscillator Enable

ValueDescription
0The oscillator is disabled.
1The oscillator is enabled.