pca8565a NXP Semiconductors, pca8565a Datasheet - Page 16

• Manufacturer Part Number: pca8565a
• Description: Real-time Clock/calendar
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA8565A_2
Product data sheet
8.6.5 Alarm flag
8.7 Register CLKOUT_control and clock output
By clearing the MSB of one or more of the alarm registers, AE_x (Alarm Enable), 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 using the
interface.
The registers at addresses 09h through 0Ch contain alarm information. When one or
more of these registers is loaded with minute, hour, day or weekday, and its corresponding
Alarm Enable bit (AE_x) is logic 0, then that information is compared with the current
minute, hour, day, and weekday. When all enabled comparisons first match, the Alarm
Flag (AF in register Control_status_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 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. Alarm registers which have their
AE_x bit at logic 1 are ignored.
Frequencies of 32.768 kHz (default), 1.024 kHz, 32 Hz, and 1 Hz can be generated for
use as a system clock, microcontroller clock, input to a charge pump, or for calibration of
the oscillator. To enable pin CLKOUT pin CLKOE must be set HIGH. When disabled,
CLKOUT is high-impedance.
Fig 7.
(1) Only when all enabled alarm settings are matching.
It’s only on increment to a matched case that the alarm flag is set, see
Alarm function block diagram
check now signal
WEEKDAY ALARM
MINUTE ALARM
WEEKDAY TIME
HOUR ALARM
MINUTE TIME
DAY ALARM
HOUR TIME
DAY TIME
Rev. 02 — 4 December 2009
=
=
=
=
AE_M
AE_W
AE_H
AE_D
set alarm flag AF
AE_M = 1
example
013aaa088
Real-time clock/calendar
Section
PCA8565A
1
0
(1)
© NXP B.V. 2009. All rights reserved.
8.6.5.
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