PCA8565BS NXP [NXP Semiconductors], PCA8565BS Datasheet - Page 11

• Manufacturer Part Number: PCA8565BS
• Description: Real time clock/calendar
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCA8565_2
Product data sheet
9.5 Data flow
Table 17.
[1]
Figure 5
If the time registers are written or read by making individual access to the chip, then there
is the risk that the time will increment between accesses. This has to be avoided by
stopping the increment of the time circuit. After access is completed, the time circuit is
allowed to continue running and any request to increment that occurred during the access
is initiated.
As a consequence of this method, it is important to read or write all time registers in one
access i.e. seconds up to years. Failing to comply with this method could result in the time
becoming corrupted.
As an example, if the time (seconds through to hours) are 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:
Bit
7 to 4 YEARS
3 to 0
1. Send a START condition and the slave address for write (A2h).
2. Set the address pointer to registers Seconds (02h).
Fig 5.
Values shown in decimal.
Symbol
shows the data flow and data dependencies starting from the 1 Hz clock tick.
Data flow for the time function
Register Years (08h) bits description
Rev. 02 — 16 June 2009
CALCULATION
LEAP YEAR
Value
0 to 9
0 to 9
[1]
[1]
Place value Description
ten’s place
unit place
SECONDS
MINUTES
MONTHS
1 Hz tick
HOURS
YEARS
DAYS
C
actual year coded in BCD format
WEEKDAY
013aaa092
Real time clock/calendar
PCA8565
© NXP B.V. 2009. All rights reserved.
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