pcf2127a NXP Semiconductors, pcf2127a Datasheet - Page 31

• Manufacturer Part Number: pcf2127a
• Description: Integrated Rtc, Tcxo And Quartz Crystal
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2127A_1
Product data sheet
8.9.8 Setting and reading the time
Figure 17
During read/write operations, the time counting circuits (memory locations 03h through
09h) are blocked.
This prevents
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/write access
is serviced. A maximum of 1 request can be stored; therefore, all accesses must be
completed within 1 second (see
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.
Fig 17. Data flow of the time function
Fig 18. Access time for read/write operations
•
•
Faulty reading of the clock and calendar during a carry condition
Incrementing the time registers during the read cycle
shows the data flow and data dependencies starting from the 1 Hz clock tick.
START
Rev. 01 — 21 January 2010
SLAVE ADDRESS
12_24 hour mode
CALCULATION
LEAP YEAR
Figure
18).
DATA
SECONDS
MINUTES
MONTHS
1 Hz tick
HOURS
YEARS
DAYS
Integrated RTC, TCXO and quartz crystal
DATA
t < 1 s
WEEKDAY
001aaf901
PCF2127A
STOP
© NXP B.V. 2010. All rights reserved.
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