PCF8564A datasheet(15/44 Pages) NXP

15 / 44 page

PCF8564A_1

Product data sheet

Rev. 1 — 8 October 2009

15 of 44

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.

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.

(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

013aaa088

WEEKDAY ALARM

AE_W

WEEKDAY TIME

DAY ALARM

AE_D

DAY TIME

HOUR ALARM

AE_H

HOUR TIME

MINUTE ALARM

AE_M

MINUTE TIME

check now signal

set alarm flag, AF(1)

AE_M= 1

example

PCF8564A 데이터시트(PDF) 15 Page - NXP Semiconductors