PCA2125TS NXP [NXP Semiconductors], PCA2125TS Datasheet - Page 12

• Manufacturer Part Number: PCA2125TS
• Description: SPI Real-time clock/calendar
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCA2125_1
Product data sheet
8.5.1 Alarm flag
Generation of interrupts from the alarm function is described in
When all enabled comparisons first match, the alarm flag bit AF is set. Bit AF will remain
set until cleared by software. Once bit AF has been cleared it will only be set again when
the time increments once more to match the alarm condition.
Alarm registers which have their bit AENx at logic 1 are ignored.
Figure 8
The flags are cleared by a write command, therefore bits 7, 6, 4, 1 and 0 must be written
with their previous values. Repeatedly re-writing these bits has no influence on the
functional behavior.
Fig 7.
Fig 8.
shows an example for clearing bit AF, but leaving bit MSF and bit TF unaffected.
Alarm function block diagram
Example where only the minute alarm is used and no other interrupts are enabled.
Alarm flag timing
check now signal
WEEKDAY ALARM
INT when AIE = 1
WEEKDAY TIME
MINUTE ALARM
minutes counter
HOUR ALARM
MINUTE TIME
DAY ALARM
HOUR TIME
DAY TIME
minute alarm
Rev. 01 — 28 July 2008
AF
44
45
=
=
=
=
WEEKDAY AEN
MINUTE AEN
HOUR AEN
DAY AEN
45
set alarm flag, AF
SPI Real-time clock/calendar
MINUTE AEN = 1
example
001aaf902
Section
001aaf903
1
0
PCA2125
46
© NXP B.V. 2008. All rights reserved.
8.7.3.
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