Atmel SAM4L-EK Atmel ATSAM4L-EK ATSAM4L-EK Data Sheet

42023E–SAM–07/2013

RCFASTCFG

Read/Write

0x00000000

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.

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.

00: 4MHz range selected.

01: 8MHz range selected.

10: 12MHz range selected.

11: Reserved.

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.

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.

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.

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.

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

7

6

5

4

3

2

1

0

FCD

NBPERIODS

-

JITMODE

TUNEEN

EN