Figure 21-5. Output Clock Switching Operation
CKR
PRESC
CLK_DPLL
DPLL_LOCK
0
1
CK STABLE
CK STABLE
CK SWITCHING
SYNCBUSY.PRESC
CK
CKDIV2
Loop Divider Ratio Updates
The DPLL Controller supports on-the-fly update of the DPLL Ratio Control (DPLLRATIO) register,
allowing to modify the loop divider ratio and the loop divider ratio fractional part when the DPLL is
enabled.
STATUS.DPLLLDRTO is set when the DPLLRATIO register has been modified and the DPLL analog cell
has successfully sampled the updated value. At that time the DPLLSTATUS.LOCK bit is cleared and set
again by hardware when the output frequency reached a stable state.
Figure 21-6. RATIOCTRL register update operation
CKR
LDR
LDRFRAC
CK
CLK_DPLL
mult0
mult1
LOCK
LOCKL
Digital Filter Selection
The PLL digital filter (PI controller) is automatically adjusted in order to provide a good compromise
between stability and jitter. Nevertheless a software operation can override the filter setting using the
Filter bit field in the DPLL Control B register (DPLLCTRLB.FILTER). The Low Power Enable bit
(DPLLCTRLB.LPEN) can be use to bypass the Time to Digital Converter (TDC) module.
21.6.7. DMA Operation
Not applicable.
21.6.8. Interrupts
The OSCCTRL has the following interrupt sources:
•
XOSCRDY - Multipurpose Crystal Oscillator Ready: A 0-to-1 transition on the STATUS.XOSCRDY
bit is detected
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
219