Datasheet
240
42023E–SAM–07/2013
ATSAM4L8/L4/L2
13.7.18 4/8/12MHz RC Oscillator Configuration Register
Name: RCFASTCFG
Access Type: Read/Write
Reset Value: 0x00000000
• CALIB: Oscillator Calibration Value
Writing a value to this field sets the oscillator trim value. A small value will produce a fast RCFAST clock and a big value will
produce a slow clock. If the tuner is enabled, writing to this field will cause the tuner to start tuning from the written value.
• LOCKMARGIN: Accepted Count Error for Lock
Writing a value to this field defines the maximum absolute value of the current count error with respect to the theoretical count
that will be trigger the RCFASTLOCK condition:
If abs(Count - Count_theor) <= LOCKMARGIN, then RCFASTLOCK is set, otherwise RCFASTLOCKLOST is set, with
Count_theor = 122 x (1 + FRANGE) << NBPERIODS.
• FRANGE: Frequency Range
00: 4MHz range selected.
01: 8MHz range selected.
10: 12MHz range selected.
11: Reserved.
• FCD: RCFAST Fuse Calibration Done
Always read as 1 (read only).
Set to 1 when the CALIB field has been updated by the Flash Fuses after a reset (read only).
0: Calibration from Flash Fuses has not been loaded. Calibration from Flash Fuses will be redone after any reset.
1: Calibration from Flash Fuses has been loaded. Calibration from Flash Fuses will only be redone after a Power-on Reset.
• NBPERIODS: Number of 32kHz Periods
Writing a value to this field defines the number of periods of the 32kHz clock used to compare the RCFAST clock output. A
higher value increases the tuner precision and smoothes the calibration adjustments.
• JITMODE: Jitter Mode
0: The RCFAST trim value is only updated when the RCFASTLOCKLOST is set; it is kept stable as long as the RCFASTLOCK
condition is set.
1: The RCFAST trim value is continuously updated.
• TUNEEN: Tuner Enable
0: Tuner is not enabled, and the RCFAST operates in open loop mode.
1: Tuner is enabled, and the RCFAST operates in closed loop mode.
• EN: Oscillator Enable
0: The RCFAST clock is disabled, and the output clock is stopped.
31 30 29 28 27 26 25 24
--------
23 22 21 20 19 18 17 16
-CALIB
15 14 13 12 11 10 9 8
LOCKMARGIN - - FRANGE
76543210
FCD NBPERIODS - JITMODE TUNEEN EN