PCF8564A datasheet(26/59 Pages) NXP

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PCA85063A

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Product data sheet

Rev. 4 — 30 March 2018

26 of 59

NXP Semiconductors

PCA85063A

Automotive Real-Time Clock/calendar with alarm function and I2C-bus

8.5.5 Register Weekday_alarm

[1]

Default value.

8.5.6 Alarm function

By clearing the alarm enable bit (AEN_x) of one or more of the alarm registers, the

corresponding alarm condition(s) are active. When an alarm occurs, AF is set logic 1. The

asserted AF can be used to generate an interrupt (INT). The AF is cleared by command.

The registers at addresses 0Bh through 0Fh contain alarm information. When one or

more of these registers is loaded with second, minute, hour, day or weekday, and its

corresponding AEN_x is logic 0, then that information is compared with the current

second, minute, hour, day, and weekday. When all enabled comparisons first match, the

alarm flag (AF in register Control_2) is set logic 1.

The generation of interrupts from the alarm function is controlled via bit AIE. If bit AIE is

enabled, the INT pin follows the condition of bit AF. AF remains set until cleared by

command. Once AF has been cleared, it will only be set again when the time increments

to match the alarm condition once more. Alarm registers which have their AEN_x bit at

logic 1 are ignored.

Table 33.

Weekday_alarm - weekday alarm register (address 0Fh) bit description

Bit

Symbol

Value

Description

AEN_W

weekday alarm

enabled

1[1]

disabled

6 to 3

unused

2to0

WEEKDAY_ALARM

0[1] to 6

weekday alarm information coded in BCD

format

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