Datasheet

59 0

2Seconds

59 0

Hours

3 4Hours

59 0 1

Seconds

Compensation event

SWCS046-016

TPS659110, TPS659112, TPS659113, TPS659116

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SWCS049L –JUNE 2010–REVISED MARCH 2014

Table 13. Real-Time Clock Registers

Example (continued)

MONTHS_REG 0x09

YEARS_REG 0x08

The user can round to the closest minute, by setting the ROUND_30S register bit. TC values are set to the

closest minute value at the next second. The ROUND_30S bit is automatically cleared when the rounding time is

performed.

Example:

• If current time is 10H59M45S, a round operation changes time to 11H00M00S.

• if current time is 10H59M29S, a round operation changes time to 10H59M00S.

8.7.2 General Registers

Software can access the RTC_STATUS_REG and RTC_CTRL_REG registers at any time (except for the

RTC_CTRL_REG[5] bit, which must be changed only when the RTC is stopped).

8.7.3 Compensation Registers

The RTC_COMP_MSB_REG and RTC_COMP_LSB_REG registers must respect the available access period.

These registers must be updated before each compensation process. For example, software can load the

compensation value into these registers after each hour event, during an available access period.

Figure 17. RTC Compensation Scheduling

This drift can be balanced to compensate for any inaccuracy of the 32-kHz oscillator. Software must calibrate the

oscillator frequency, calculate the drift compensation versus 1-hour time period; and then load the compensation

registers with the drift compensation value. Indeed, if the AUTO_COMP_EN bit in the RTC_CTRL_REG is

enabled, the value of COMP_REG (in twos-complement) is added to the RTC 32-kHz counter at each hour and 1

second. When COMP_REG is added to the RTC 32-kHz counter, the duration of the current second becomes

(32768 – COMP_REG)/32768s; so, the RTC can be compensated with a 1/32768 s/hour time unit accuracy.

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