PCF8564A datasheet(24/59 Pages) NXP

24 / 59 page

PCA85063A

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Product data sheet

Rev. 4 — 30 March 2018

24 of 59

NXP Semiconductors

PCA85063A

Automotive Real-Time Clock/calendar with alarm function and I2C-bus

Because of this method, it is very important to make a read or write access in one go, that

is, setting or reading 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 will increment 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.

Recommended method for reading the time:

1. Send a START condition and the slave address (see Table 39 on page 33) for write

(A2h)

2. Set the address pointer to 4 (Seconds) by sending 04h

3. Send a RESTART condition or STOP followed by START

4. Send the slave address for read (A3h)

5. Read Seconds

6. Read Minutes

7. Read Hours

8. Read Days

9. Read Weekdays

10. Read Months

11. Read Years

12. Send a STOP condition

8.5 Alarm registers

8.5.1 Register Second_alarm

[1]

Default value.

Fig 13. Access time for read/write operations

Table 29.

Second_alarm - second alarm register (address 0Bh) bit description

Bit

Symbol

Value

Place value Description

AEN_S

second alarm

enabled

1[1]

disabled

6 to 4

SECOND_ALARM

0[1] to 5

ten’s place

second alarm information

coded in BCD format

3 to 0

0[1] to 9

unit place

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