Datasheet

Table 17-7. Start-Up Time for 32kHz Internal Oscillator
STARTUP[2:0] Number of OSC32K clock cycles Approximate Equivalent Time
(OSCULP= 32 kHz)
(1)(2)(3)
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
SAM D21 Family
SYSCTRL – System Controller
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 217