12.5.11 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 or not, 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 and Idle sleep modes (1) |
1 | The XOSC32K oscillator will always run in Active, Idle, Standby and Power-Down sleep modes (2) |
Bits 5:4 – CSUT[1:0] Crystal Start-Up Time
This bit field controls the start-up time of the 32.768 kHz Crystal Oscillator
(XOSC32K) 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 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 by
disabling 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 or not.
Value | Description |
---|---|
0 | The XOSC32K oscillator is disabled |
1 | The XOSC32K oscillator is enabled and overrides normal port operation for the respective oscillator pins |