SAM4L Datasheet, PDF (234/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
13.7.18 4/8/12MHz RC Oscillator Configuration Register
Name:
RCFASTCFG
Access Type:
Read/Write
Reset Value:
0x00000000
31
30
29
28
27
26
25
24
-
-
-
-
-
-
-
-
23
22
21
20
19
18
17
16
-
CALIB
15
14
13
12
11
10
LOCKMARGIN
-
-
9
8
FRANGE
7
FCD
6
5
4
NBPERIODS
3
2
1
0
-
JITMODE
TUNEEN
EN
• 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.
42023C–SAM–02/2013
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