PCF85263ATLSLASHA datasheet(18/102 Pages) NXP

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NXP Semiconductors

PCF85263A

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

• Write data (clear STOP, 00h). Time starts counting from this point

• I2C STOP condition

7.3 Stop-watch mode time registers

These registers are coded in the BCD format to simplify application use.

Stop-watch mode is enabled by setting RTCM = 1. In stop-watch mode, the PCF85263A counts from 100th

seconds to 99 9 999 hours. There are no day, weekday, month, or year registers.

The default state is:

Time:

00 00 00:00:00.00

Monitor bits:

OS = 1, EMON = 0 (for details, see Section 7.2.2 and Section 7.2.3)

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

03h

Hours_xx_xx_00

0 to 9

04h

Hours_xx_00_xx

0 to 9

05h

Hours_00_xx_xx

0 to 9

06h

Not used

07h

Not used

Table 11. Time registers in stop-watch mode (RTCM = 1)

[1]

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

7.3.1 Setting and reading the time in stop-watch mode

Figure 12 shows the data flow and data dependencies starting from the 100 Hz clock tick.

During read operations, the time counting circuits (memory locations 00h through 07h) are copied into an output

When reading or writing the time, it is important to make a read or write access in one go, that is, setting or

reading 100th_seconds through to HR_00_xx_xx must be made in one single access. Failing to comply with this

method could result in the time becoming corrupted.

As an example, if the seconds value is set in one access and then in a following access the minutes value is

set, it is possible that the time increments between the two accesses. A similar problem exists when reading.

A roll-over can occur between reads. therefore giving the seconds from one moment and the minutes from the

next.

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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