PCF2129T Datasheet, PDF (27/73 Pages) NXP Semiconductors – Accurate RTC with integrated quartz crystal for industrial

NXP Semiconductors
PCF2129T
Accurate RTC with integrated quartz crystal for industrial
1 Hz tick
SECONDS
MINUTES
12_24 hour mode
LEAP YEAR
CALCULATION
HOURS
DAYS
MONTHS
WEEKDAY
YEARS
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Fig 13. Data flow of the time function
After this read/write access is completed, the time circuit is released again. 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 Figure 14).
t<1s
START SLAVE ADDRESS
DATA
DATA
Fig 14. Access time for read/write operations
STOP
013aaa215
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. Therefore it is
advised to read all time and date registers in one access.
PCF2129T
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 12 February 2013
© NXP B.V. 2013. All rights reserved.
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