12.5.8 External 32.768 kHz Crystal Oscillator Control A
| Name: | XOSC32KCTRLA |
| Offset: | 0x1C |
| Reset: | 0x00 |
| Property: | Configuration Change Protection |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| RUNSTDBY | CSUT[1:0] | SEL | LPMODE | ENABLE | |||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | |||
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | |||
Bit 7 – RUNSTDBY Run Standby
This bit controls whether the 32.768 kHz Crystal Oscillator (XOSC32K) is always
running and in which modes when the ENABLE bit is ‘
1’.Note:
- The requesting peripheral, or the main clock, must take the oscillator start-up time into account.
- The oscillator signal is only available if requested and will be available after a maximum of three XOSC32K cycles if the initial crystal start-up time has already ended.
| Value | Description |
|---|---|
| 0 | The XOSC32K oscillator will only run when requested by a peripheral or by the main clock in Active mode and Idle sleep mode (1) |
| 1 | The XOSC32K oscillator will always run in Active mode, Idle sleep mode, Standby sleep mode and Power-Down sleep mode (2) |
Bits 5:4 – CSUT[1:0] Crystal Start-Up Time
This bit field controls the 32.768 kHz Crystal Oscillator (XOSC32K) start-up time
when the Source Select (SEL) bit is ‘
0’.Note: This
bit field is read-only when the ENABLE bit or the XOSC32K Status (XOSCS) bit
in the Main Clock Status (CLKCTRL.MCLKSTATUS) register is
‘
1’. | Value | Name | Description |
|---|---|---|
| 0x0 | 1K | 1k cycles |
| 0x1 | 16K | 16k cycles |
| 0x2 | 32K | 32k cycles |
| 0x3 | 64K | 64k cycles |
Bit 2 – SEL Source Select
This bit controls the source of the 32.768 kHz Crystal Oscillator (XOSC32K).
Note: This bit field is read-only when the ENABLE bit or the
XOSC32K Status (XOSCS) bit in the Main Clock Status (CLKCTRL.MCLKSTATUS)
register is ‘
1’. | Value | Description |
|---|---|
| 0 | External crystal connected to the XTAL32K1 and XTAL32K2 pins |
| 1 | External clock on the XTAL32K1 pin |
Bit 1 – LPMODE Low-Power Mode
Note: Enabling the Low-Power mode can
increase the crystal’s start-up time. Mitigate this by altering the crystal
implementation to reduce serial resistance and overall capacitance or disabling
the Low-Power mode.
| Value | Description |
|---|---|
| 0 | The Low-Power mode is disabled |
| 1 | The Low-Power mode is enabled |
Bit 0 – ENABLE Enable
This bit controls whether the 32.768 kHz Crystal Oscillator (XOSC32K) is enabled.
| Value | Description |
|---|---|
| 0 | The XOSC32K oscillator is disabled |
| 1 | The XOSC32K oscillator is enabled and overrides ordinary port operation for the respective oscillator pins |