Datasheet

31.20.9 PMC Clock Generator Main Clock Frequency Register
Name: CKGR_MCFR
Offset: 0x0024
Reset: 0x00000000
Property: Read/Write
This register can only be written if the WPEN bit is cleared in the PMC W
rite Protection Mode Register.
Bit 31 30 29 28 27 26 25 24
CCSS
Access
Reset 0
Bit 23 22 21 20 19 18 17 16
RCMEAS MAINFRDY
Access
Reset 0 0
Bit 15 14 13 12 11 10 9 8
MAINF[15:8]
Access
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
MAINF[7:0]
Access
Reset 0 0 0 0 0 0 0 0
Bit 24 – CCSS Counter Clock Source Selection
Value Description
0
The measured clock of the MAINF counter is the Main RC oscillator.
1
The measured clock of the MAINF counter is the Main crystal oscillator.
Bit 20 – RCMEAS RC Oscillator Frequency Measure (write-only)
The measurement is performed on the main frequency (i.e., not limited to the Main RC oscillator only). If the source
of MAINCK is the Main crystal oscillator
, the restart of measurement may not be required because of the stability of
crystal oscillators.
Value Description
0
No effect.
1
Restarts measuring of the frequency of MAINCK. MAINF carries the new frequency as soon as a low-
to-high transition occurs on the MAINFRDY flag.
Bit 16 – MAINFRDY Main Clock Frequency Measure Ready
Value Description
0
MAINF value is not valid or the measured oscillator is disabled or a measure has just been started by
means of RCMEAS.
1
The measured oscillator has been enabled previously and MAINF value is available.
Note: T
o ensure that a correct value is read on the MAINF field, the MAINFRDY flag must be read at ‘1’
then another read access must be performed on the register to get a stable value on the MAINF field.
Bits 15:0 – MAINF[15:0] Main Clock Frequency
Gives the number of cycles of the clock selected by the bit CCSS within 16 SLCK periods. T
o calculate the frequency
of the measured clock:
f
SELCLK
= (MAINF x f
SLCK
)/16
where frequency is in MHz.
SAM E70/S70/V70/V71 Family
Power Management Controller (PMC)
©
2019 Microchip Technology Inc.
Datasheet
DS60001527D-page 274