26.6.2 RTC Mode Register


Bit	31	30	29	28	27	26	25	24
			TPERIOD[1:0]			THIGH[2:0]
Access			R/W	R/W		R/W	R/W	R/W
Reset			0	0		0	0	0


Bit	23	22	21	20	19	18	17	16
		OUT1[2:0]				OUT0[2:0]
Access		R/W	R/W	R/W		R/W	R/W	R/W
Reset		0	0	0		0	0	0


Bit	15	14	13	12	11	10	9	8
	HIGHPPM	CORRECTION[6:0]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0


Bit	7	6	5	4	3	2	1	0
				NEGPPM		UTC	PERSIAN	HRMOD
Access				R/W		R/W	R/W	R/W
Reset				0		0	0	0

Bits 29:28 – TPERIOD[1:0] Period of the Output Pulse

Value	Name	Description
0	P_1S	1 second
1	P_500MS	500 ms
2	P_250MS	250 ms
3	P_125MS	125 ms

Bits 26:24 – THIGH[2:0] High Duration of the Output Pulse

Value	Name	Description
0	H_31MS	31.2 ms
1	H_16MS	15.6 ms
2	H_4MS	3.91 ms
3	H_976US	976 μs
4	H_488US	488 μs
5	H_122US	122 μs
6	H_30US	30.5 μs
7	H_15US	15.2 μs

Bits 22:20 – OUT1[2:0] ADC Last Channel Trigger Event Source Selection

Value	Name	Description
0	NO_WAVE	No waveform, stuck at ‘0’
1	FREQ1HZ	1 Hz square wave
2	FREQ32HZ	32 Hz square wave
3	FREQ64HZ	64 Hz square wave
4	FREQ512HZ	512 Hz square wave
5	ALARM_TOGGLE	Output toggles when alarm flag rises
6	ALARM_FLAG	Output is a copy of the alarm flag
7	PROG_PULSE	Duty cycle programmable pulse

Bits 18:16 – OUT0[2:0] All ADC Channel Trigger Event Source Selection

Value	Name	Description
0	NO_WAVE	No waveform, stuck at ‘0’
1	FREQ1HZ	1 Hz square wave
2	FREQ32HZ	32 Hz square wave
3	FREQ64HZ	64 Hz square wave
4	FREQ512HZ	512 Hz square wave
5	ALARM_TOGGLE	Output toggles when alarm flag rises
6	ALARM_FLAG	Output is a copy of the alarm flag
7	PROG_PULSE	Duty cycle programmable pulse

Bit 15 – HIGHPPM HIGH PPM Correction

If the absolute value of the correction to be applied is lower than 30 ppm, it is recommended to clear HIGHPPM. HIGHPPM set to 1 is recommended for 30 ppm correction and above.

Formula:

If HIGHPPM = 0, then the clock frequency correction range is from 1.5 ppm up to 98 ppm. The RTC accuracy is less than 1 ppm for a range correction from 1.5 ppm up to 30 ppm.

The correction field must be programmed according to the required correction in ppm; the formula is as follows:

CORRECTION = \frac{3906}{20 \times ppm} - 1

The value obtained must be rounded to the nearest integer prior to being programmed into CORRECTION field.

If HIGHPPM = 1, then the clock frequency correction range is from 30.5 ppm up to 1950 ppm. The RTC accuracy is less than 1 ppm for a range correction from 30.5 ppm up to 90 ppm.

The correction field must be programmed according to the required correction in ppm; the formula is as follows:

CORRECTION = \frac{3906}{ppm} - 1

The value obtained must be rounded to the nearest integer prior to be programmed into CORRECTION field.

If NEGPPM is set to 1, the ppm correction is negative (used to correct crystals that are faster than the nominal 32.768 kHz).

Value	Name	Description
0	DISABLED	Lower range ppm correction with accurate correction (below 30ppm correction).
1	ENABLED	Higher range ppm correction with accurate correction (higher than 30ppm correction).

Bits 14:8 – CORRECTION[6:0] Slow Clock Correction

Value	Name	Description
0	DISABLED	No correction
1–127	–	The slow clock will be corrected according to the formula given in HIGHPPM description.

Bit 4 – NEGPPM Negative PPM Correction

See CORRECTION and HIGHPPM field descriptions.

NEGPPM must be cleared to correct a crystal slower than 32.768 kHz.

Value	Name	Description
0	DISABLED	Positive correction (the divider will be slightly higher than 32768).
1	ENABLED	Negative correction (the divider will be slightly lower than 32768).