PCF85263ATLSLASHA datasheet(10/102 Pages) NXP

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NXP Semiconductors

PCF85263A

Tiny RTC/Calendar with Alarm Function, Battery Switch-Over, Time Stamp Input, and I2C-bus

7 Functional description

The PCF85263A contains 8-bit registers for time information, for timestamp information and registers for

system configuration. Included is an auto-incrementing register address, an on-chip 32.768 kHz oscillator

with integrated capacitors, a frequency divider providing the source clock for the Real-Time Clock (RTC), and

calender, and an I2C-bus interface with a maximum data rate of 400 kbit/s.

The built-in address register will increment automatically after each read or write of a data byte. After register

2Fh, the auto-incrementing will wrap around to address 00h (for details, see Figure 7).

aaa-009084

address register

00h

auto-increment

wrap around

01h

02h

03h

...

2Dh

2Eh

2Fh

Figure 7. Address register incrementing

All registers (see Table 4, Table 5, and Table 6) are designed as addressable 8-bit parallel registers although not

all bits are implemented. Figure 8 gives an overview of the address map.

Time registers

Alarm registers

Offset register

RAM byte

Watchdog

Stop and reset

Timestamp registers

Function setting

00h

07h

08h

10h

11h

23h

25h

2Bh

24h

2Ch

2Dh

2Eh

2Fh

aaa-009114

Figure 8. Register map

The 100th seconds, seconds, minutes, hours, days, months, and years and the corresponding alarm registers

are all coded in Binary Coded Decimal (BCD) format. When one of the RTC registers is read, the contents

of all-time counters are frozen. Therefore, faulty reading of the clock and calendar during a carry condition is

prevented.

PCF85263A

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 5.4 — 12 December 2025

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