PCF2129AT datasheet(28/68 Pages) NXP

28 / 68 page

PCF2129A_1

Product data sheet

Rev. 01 — 13 January 2010

28 of 68

NXP Semiconductors

PCF2129A

Integrated RTC, TCXO and quartz crystal

8.9.4 Register Day_alarm

[1]

Default value.

8.9.5 Register Weekday_alarm

[1]

Default value.

8.9.6 Alarm flag

When all enabled comparisons first match, the alarm flag AF (register Control_2) is set.

AF will remain set until cleared by using the interface. Once AF has been cleared it will

only be set again when the time increments to match the alarm condition once more. For

clearing the flags see Section 8.10.5

Alarm registers which have their alarm enable bit AE_x at logic 1 are ignored.

Table 28.

Day_alarm - day rearm register (address 0Dh) bit description

Bit

Symbol

Value

Place value Description

AE_D

day alarm is enabled

1[1]

day alarm is disabled

unused

5 to 4 DAY_ALARM

0 to 3

ten’s place

day alarm information coded in BCD

format

3to0

0to9

unit place

Table 29.

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

Bit

Symbol

Value

Description

AE_W

weekday alarm is enabled

1[1]

weekday alarm is disabled

6to3 -

unused

2 to 0 WEEKDAY_ALARM

0 to 6

weekday alarm information

Example where only the minute alarm is used and no other interrupts are enabled.

Fig 16. Alarm flag timing diagram

001aaf903

minute alarm

minutes counter

INT when AIE = 1

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