PCF85263ATLSLASHAX datasheet(14/102 Pages) NXP

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NXP Semiconductors

PCF85263A

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

Bit positions labeled as - are not implemented. After reset, all registers are set according to Table 61.

Bit

Address

Reference

2Eh

Stop_enable

STOP

Section 7.16

Reset

2Fh

Resets

CPR

CTS

Section 7.15

Table 6. Control and function registers overview...continued

7.2 RTC mode time and date registers

RTC mode is enabled by setting RTCM = 0. These registers are coded in the BCD format to simplify application

use.

The default state is:

Time: 00:00:00.00

Date: 2000 01 01

Weekday: Saturday

Monitor bits: OS = 1, EMON = 0

Bit positions labeled as - are not implemented and return 0 when read.

Upper-digit (ten’s place)

Digit (unit place)

Address

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

00h

100th_seconds [1]

0 to 9

01h

Seconds

0 to 5

0 to 9

02h

Minutes

EMON

0 to 5

0 to 9

AMPM 0 to 1

0 to 9

03h

Hours [2]

0 to 2

0 to 9

04h

Days [3]

0 to 3

0 to 9

05h

Weekdays

0 to 6

06h

Months

0 to 1

0 to 9

07h

Years

0 to 9

Table 7. Time and date registers in RTC mode (RTCM = 0)

[1]

The 100th_seconds register is only available when the 100TH mode is enabled, see Section 7.13.1. When the 100TH mode is disabled, this register

always returns 0.

[2]

Hour mode is set by the 12_24 bit in the Oscillator register, see Section 7.10.

[3]

If the year counter contains a value, which is exactly divisible by 4, the PCF85263A compensates for leap years by adding a 29th day to February.

7.2.1 Definition of BCD

The Binary-Coded Decimal (BCD) is an encoding of numbers where each digit is represented by a separate

bit field. Each bit field can only contain the values 0 to 9. In this way, decimal numbers and counting is

implemented.

Example: 59 encoded as an entire number is represented by 3Bh or 11 1011. In BCD, the 5 is represented as

5h or 0101 and the 9 as 9h or 1001, which combines to 59h.

PCF85263A

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Product data sheet

Rev. 5.4 — 12 December 2025

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