16.8.7 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.
| STARTUP[2:0] | Number of OSC32K clock cycles | Approximate Equivalent Time |
|---|---|---|
| 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, 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.
| 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. |
Bit 2 – EN32K 32kHz Output Enable
| Value | Description |
|---|---|
| 0 | The 32kHz output is disabled. |
| 1 | The 32kHz output is enabled. |
| 0 | The oscillator is disabled. |
| 1 | The oscillator is enabled. |
Bit 1 – ENABLE Oscillator Enable
| Value | Description |
|---|---|
| 0 | The oscillator is disabled. |
| 1 | The oscillator is enabled. |