PCF85263ATLSLASHAX datasheet(19/100 Pages) NXP

19 / 100 page

PCF85263A

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Product data sheet

Rev. 4.1 — 27 November 2015

19 of 100

NXP Semiconductors

PCF85263A

Tiny RTC with alarm, battery switch-over, and I2C-bus

When reading or writing the time it is very important to make a read or write access in one

go, that is, setting or reading 100th_seconds through to HR_00_xx_xx should 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 may occur between reads thus giving

the seconds from one moment and the minutes from the next.

8.4 Alarms

There are two independent alarms. Each is separately configured and may be used to

generate an interrupt. In RTC mode, an alarm is configured for time and date. In

stop-watch mode when the RTC is functioning as an elapsed time counter, an alarm is

configured for time only.

8.4.1 Alarms in RTC mode

In RTC mode, Alarm 1 can be configured from seconds to months. Alarm 2 operates on

minutes, hours and weekday. Each segment of the time is independently enabled. Alarms

can be output on the INTA and INTB pins.

8.4.1.1

Alarm1 and alarm2 registers in RTC mode

Setting the time for alarm1: Only the information which is relevant for the alarm condition

must to be programmed. The unused parts are ignored.

Fig 11. Data flow for the stop-watch function

PCF85263ATL/AX Datasheet(PDF) 19 Page - NXP Semiconductors