PCF8564A_10 Datasheet, PDF (15/45 Pages) NXP Semiconductors – Real time clock and calendar

NXP Semiconductors
PCF8564A
Real time clock and calendar
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 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.
check now signal
MINUTE ALARM
=
MINUTE TIME
HOUR ALARM
=
HOUR TIME
DAY ALARM
=
DAY TIME
AE_M
AE_H
AE_D
example
AE_M = 1
1
0
set alarm flag AF ⁽¹⁾
WEEKDAY ALARM
=
WEEKDAY TIME
AE_W
013aaa088
(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 Section 8.6.5.
Fig 8. Alarm function block diagram
8.7 Register CLKOUT_ctrl and clock output
A programmable square wave is available at pin CLKOUT. Operation is controlled by the
FE bit in register CLKOUT_ctrl at address 0Dh and the CLKOUT output enable pin
(CLKOE). To enable pin CLKOUT pin CLKOE must be set HIGH.
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.
PCF8564A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 02 — 30 September 2010
© NXP B.V. 2010. All rights reserved.
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