CKGR_MCFR

PMC Clock Generator Main Clock Frequency Register

This register can only be written if the WPEN bit is cleared in the PMC Write Protection Mode Register.

0x0024 32 Read/Write 0x00000000

PMC Clock Generator Main Clock Frequency Register
MAINF
Main Clock Frequency
MAINFRDY
Main Clock Frequency Measure Ready
RCMEAS
RC Oscillator Frequency Measure (write-only)
CCSS
Counter Clock Source Selection

PMC Clock Generator Main Clock Frequency 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

Bits 15:0 – MAINF[15:0]: Main Clock Frequency

Main Clock Frequency

Gives the number of cycles of the clock selected by the bit CCSS within 16 SLCK periods. To calculate the frequency of the measured clock:

f_SELCLK = (MAINF x f_SLCK)/16

where frequency is in MHz.

Bit 16 – MAINFRDY: Main Clock Frequency Measure Ready

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: To 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.

Value

Description

MAINF value is not valid or the measured oscillator is disabled or a measure has just been started by means of RCMEAS.

The measured oscillator has been enabled previously and MAINF value is available.

Note: To 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.

Bit 20 – RCMEAS: RC Oscillator Frequency Measure (write-only)

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 24 – CCSS: Counter Clock Source Selection

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.