pcf8564a NXP Semiconductors, pcf8564a Datasheet - Page 13

• Manufacturer Part Number: pcf8564a
• Description: Real Time Clock And Calendar
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF8564A_1
Product data sheet
8.6.1 Register Minute_alarm
8.6 Alarm registers
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:
10. Read the century and month.
11. Read the years.
12. Send a STOP condition.
Table 18.
[1]
Bit
7
6 to 4 MINUTE_ALARM
3 to 0
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.
Fig 7.
Default value.
Symbol
AE_M
Access time for read/write operations
Minute_alarm - minute alarm register (address 09h) bit description
Rev. 1 — 8 October 2009
START
Value
0
1
0 to 5
0 to 9
[1]
slave address
Place value Description
-
-
ten’s place
unit place
data
minute alarm is enabled
minute alarm is disabled
minute alarm information coded in BCD
format
data
t < 1 s
data
Real time clock and calendar
STOP
013aaa215
PCF8564A
© NXP B.V. 2009. All rights reserved.
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