PCF8564A_1308 Datasheet, PDF (13/48 Pages) NXP Semiconductors – Real time clock and calendar

NXP Semiconductors
PCF8564A
Real time clock and calendar
WV
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Fig 6. Access time for read/write operations
6723
DDD
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 (seconds) by sending 02h.
3. Send a RE-START condition or STOP followed by START.
4. Send the slave address for read (A3h).
5. Read the seconds.
6. Read the minutes.
7. Read the hours.
8. Read the days.
9. Read the weekdays.
10. Read the century and month.
11. Read the years.
12. Send a STOP condition.
8.6 Alarm registers
8.6.1 Register Minute_alarm
Table 19. Minute_alarm - minute alarm register (address 09h) bit description
Bit Symbol
Value Place value Description
7
AEN_M
0
-
minute alarm is enabled
1^[1]
-
minute alarm is disabled
6 to 4 MINUTE_ALARM
3 to 0
0 to 5
0 to 9
ten’s place minute alarm information coded in BCD
unit place ^format
[1] Default value.
PCF8564A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 26 August 2013
© NXP B.V. 2013. All rights reserved.
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