PCF85263ATLSLASHAX datasheet(59/102 Pages) NXP

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NXP Semiconductors

PCF85263A

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

The STOP bit stops the time from counting in both RTC mode and stop-watch mode. For RTC mode, STOP is

useful to set the time accurately. For stop-watch mode, it is the start/stop control for the watch.

The counter can also be controlled from the TS pin by configuring STOPM in the Function register

(Section 7.13). The internal stop signal is a combination of STOP and the TS pin state.

STOP bit

TS pin [1] [2]

stop signal

Counter

Stopped

Running

Table 63. Counter stop signal

[1]

It requires STOPM and TSPM[1:0] to be configured.

[2]

TSL = 0 (active HIGH) (Pin_IO register, address 27h).

aaa-010477

OSCILLATOR

OSCILLATOR STOP

DETECTOR

setting the OS flag

div 4

32768 Hz

8192 Hz

stop(1)

PRESCALER

RESET

100 Hz tick

1 Hz tick

CPR

1. stop is a combination of the STOP register bit and the TS pin when programmed for stop control.

Figure 32. CPR and STOP bit functional diagram

The stop signal blocks the 8.192 kHz clock from generating system clocks and freezes the time. In this state,

the prescaler can be cleared with the CPR command in the Resets register (Section 7.15).

Remark: The output of clock frequencies is not affected.

The time circuits can then be set and do not increment until the STOP bit is released.

The stop acts on the 8.192 kHz signal. And because the I2C-bus or TS pin input is asynchronous to the crystal

oscillator, the accuracy of restarting the time circuits is between zero and one 8.192 kHz cycle (see Figure 33).

aaa-004417

0 µs to 122 µs

8192 Hz

stop released

Figure 33. STOP release timing

The first increment of the time circuits is between 0 s and 122 μs after STOP is released.

The flow for accurately setting the time in RTC mode is:

• Start an I2C access at register 2Eh

• Set the STOP bit

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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