PCF8563TSLASH5 datasheet(13/45 Pages) NXP

13 / 45 page

PCF8563

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Product data sheet

Rev. 11 — 26 October 2015

13 of 45

NXP Semiconductors

PCF8563

Real-time clock/calendar

After this read/write access is completed, the time circuit is released again and any

pending request to increment the time counters that occurred during the read access is

serviced. A maximum of 1 request can be stored; therefore, all accesses must be

completed within 1 second (see Figure 8).

As a consequence 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 may 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 for write (A2h).

2. Set the address pointer to 2 (VL_seconds) by sending 02h.

3. Send a RESTART condition or STOP followed by START.

4. Send the slave address for read (A3h).

5. Read VL_seconds.

6. Read Minutes.

7. Read Hours.

8. Read Days.

9. Read Weekdays.

10. Read Century_months.

11. Read Years.

12. Send a STOP condition.

8.6 Alarm registers

8.6.1 Register Minute_alarm

Fig 8.

Access time for read/write operations

t < 1 s

013aaa215

SLAVE ADDRESS

DATA

STOP

DATA

START

Table 18.

Minute_alarm - minute alarm register (address 09h) bit description

Bit

Symbol

Value

Place value Description

AE_M

minute alarm is enabled

1[1]

minute alarm is disabled

6 to 4 MINUTE_ALARM

0 to 5

ten’s place

minute alarm information coded in BCD

format

3 to 0

0 to 9

unit place

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