Atmel Xplained Pro Evaluation Kit for the ATSAMD21J18A Microcontroller ATSAMD21-XPRO ATSAMD21-XPRO Data Sheet
Product codes
ATSAMD21-XPRO
178
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181C–SAM-D21_Datasheet–07/2014
z
Bit 11 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
z
Bits 10:8 – STARTUP[2:0]: Oscillator Start-Up Time
These bits select start-up time for the oscillator according to
These bits select start-up time for the oscillator according to
.
The OSCULP32K oscillator is used as input clock to the startup counter.
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.
3. Start-up time is n OSC32K cycles + 2 OSC32K cycles.
z
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.
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 oscilla-
tor is disabled if no peripheral is requesting the clock source.
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.
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 oscilla-
tor is disabled if no peripheral is requesting the clock source.
z
Bit 6 – RUNSTDBY: Run in Standby
This bit controls how the OSC32K behaves during standby sleep mode:
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.
This bit controls how the OSC32K behaves during standby sleep mode:
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.
Table 16-10. Start-Up Time for 32kHz Internal Oscillator
STARTUP[2:0]
Number of OSC32K
clock cycles
clock cycles
Approximate Equivalent Time
(OSCULP= 32 kHz)
(OSCULP= 32 kHz)
0x0
3
92µs
0x1
4
122µs
0x2
6
183µs
0x3
10
305µs
0x4
18
549µs
0x5
34
1038µs
0x6
66
2014µs
0x7
130
3967µs