PCF8523 datasheet(13/66 Pages) NXP

13 / 66 page

PCF8523

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Product data sheet

Rev. 3 — 30 March 2011

13 of 66

NXP Semiconductors

PCF8523

Real-Time Clock (RTC) and calendar

When SIE, CTAIE, WTAIE, CTBIE, AIE, CIE, BSIE, BLIE, and clock-out are disabled, then INT1 will remain high-impedance.

When CTBIE is disabled, then INT2 will remain high-impedance.

Fig 8.

Interrupt block diagram

BLF: BATTERY

LOW FLAG

SET

set battery

low flag, BLF

to interface:

read BLF

BLIE

013aaa330

from battery

low detection

circuit: clear BLF

CLEAR

BSF: BATTERY

FLAG

SET

set battery

flag, BSF

to interface:

read BSF

BSIE

from interface:

clear BSF

CLEAR

PULSE

GENERATOR 5

SET

offset circuit:

add/subtract pulse

CIE

from interface:

clear CIE

CLEAR

AF: ALARM

FLAG

SET

set alarm

flag, AF

to interface:

read AF

AIE

from interface:

clear AF

CLEAR

WTAF:

WATCH DOG

TIMER FLAG

SET

WATCHDOG

COUNTER A

to interface:

read WTAF

MCU loading

watchdog counter

or reading WTAF

CLEAR

CTAF:

COUNTDOWN

TIMER A FLAG

SET

COUNTDOWN

COUNTER A

to interface:

read CTAF

CTAIE

INT1

from interface:

clear CTAF

CLEAR

PULSE

GENERATOR 2

TRIGGER CLEAR

SF:

SECOND FLAG

SET

SECONDS COUNTER

to interface:

read SF

SIE

from interface:

clear SF

CLEAR

SIE

PULSE

GENERATOR 1

TRIGGER CLEAR

TAM

CLKOUT

INT1/CLKOUT

ENABLE

TAC = 01

ENABLE

TAC = 10

PULSE

GENERATOR 3

TRIGGER CLEAR

WTAIE

TAM

CTBF:

COUNTDOWN

TIMER B FLAG

SET

COUNTDOWN

COUNTER B

to interface:

read CTBF

CTBIE

from interface:

clear CTBF

CLEAR

PULSE

GENERATOR 4

TRIGGER CLEAR

TBM

ENABLE

TBC = 1

INT2

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