PCF2123 datasheet(33/86 Pages) NXP

33 / 86 page

NXP Semiconductors

PCA2131

Nano-power highly accurate RTC with integrated quartz crystal for automotive applications

As an example, a roll-over may occur between reads thus giving the minutes from one

moment and the hours from the next. Therefore it is advised to read all time and date

registers in one access.

7.10 Alarm function

When one or more of the alarm bit fields are loaded with a valid second, minute, hour,

day, or weekday and its corresponding alarm enable bit (AE_x) is logic 0, then that

information is compared with the actual second, minute, hour, day, and weekday (see

Figure 14).

013aaa236

WEEKDAY ALARM

AE_W

WEEKDAY TIME

DAY ALARM

AE_D

DAY TIME

HOUR ALARM

AE_H

HOUR TIME

MINUTE ALARM

check now signal

set alarm flag AF (1)

AE_S = 1

example

AE_M

MINUTE TIME

SECOND TIME

SECOND ALARM

AE_S

1. Only when all enabled alarm settings are matching.

Figure 14. Alarm function block diagram

The generation of interrupts from the alarm function is described in Section 7.13.4.

7.10.1 Register Second_alarm

Bits labeled as X are undefined at power-on and unchanged by subsequent resets.

Bit

Symbol

AE_S

SECOND_ALARM (0 to 59)

Reset

value

Table 45. Second_alarm - second alarm register (address 0Eh) bit allocation

PCA2131

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 1.0 — 26 July 2021

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