PCF85263ATLSLASHA datasheet(17/100 Pages) NXP

17 / 100 page

PCF85263A

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Product data sheet

Rev. 4.1 — 27 November 2015

17 of 100

NXP Semiconductors

PCF85263A

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

8.2.6 Setting and reading the time in RTC mode

Figure 10 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 register. The RTC continues counting in the background.

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 years 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 time (seconds through to hours) is set in one access and then in a

second access the date 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 minutes from one moment and the hours from the next.

Before setting the time, the STOP bit should be set and the prescalers should be cleared

(see Section 8.16 “Stop_enable register” on page 60).

An example of setting the time: 14 hours, 23 minutes and 19 seconds.

• I2C START condition

• I2C slave address + write (A2h)

• register address (2Eh)

• write data (set STOP, 01h)

Fig 10. Data flow for the time function

PCF85263ATL/A Datasheet(PDF) 17 Page - NXP Semiconductors