PCF85263ATSLASHA datasheet(26/102 Pages) NXP

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NXP Semiconductors

PCF85263A

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

A1F and A2F remain set until cleared by command. Once an alarm flag has been cleared, it is only set again

when the time increments to match the alarm condition once more.

When an interrupt pin is configured to pulse mode and if an alarm flag is not cleared and the time increments to

match the alarm condition again, then a repeated interrupt pulse is generated.

7.5 Watchdog

Bit

Symbol

Value

Description

Watchdog mode

0 [1]

Single shot

WDM

Repeat mode

Watchdog register bits

0h [1] to 1Fh

Write: Watchdog counter load value

6 to 2

WDR[4:0]

0h to 1Fh

Read: current counter value

Watchdog step size (source clock)

00 [1]

4 seconds (0.25 Hz)

1 second (1 Hz)

1⁄4 second (4 Hz)

1 to 0

WDS[1:0]

1⁄16 second (16 Hz)

Table 16. Watchdog - Watchdog control and register (address 2Dh) bit description

[1]

Default value.

7.5.1 Watchdog functions

The Watchdog has four selectable step sizes allowing for periods in the range from 62.5 ms to 124 seconds. For

periods greater than 2 minutes, the alarm function can be used.

(1)

Delay

WDS[1:0]

Watchdog step size

[1]

Minimum Watchdog duration

WDR = 1

Maximum Watchdog duration

WDR = 31

4 s

124 s

1 s

31 s

1⁄4 s

0.25 s

7.75 s

1⁄16 s

0.0625 s

1.9375 s

Table 17. Watchdog durations

[1]

Time periods can be affected by correction pulses.

Remark: All timings are generated from the 32.768 kHz oscillator and are based on the assumption that there is

0 ppm deviation. Deviation in oscillator frequency results in deviation in timings. It is not applicable to interface

timing.

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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