PCF8563
NXP Semiconductors
Real-time clock/calendar
8.4.7 Register Years
Table 17. Years - years register (08h) bit description
Bit
Symbol
Value
0 to 9
0 to 9
Place value Description
7 to 4 YEARS
3 to 0
ten’s place actual year coded in BCD format[1]
unit place
[1] When the register Years overflows from 99 to 00, the century bit C in the register Century_months is
toggled.
8.5 Setting and reading the time
Figure 8 shows the data flow and data dependencies starting from the 1 Hz clock tick.
1 Hz tick
SECONDS
MINUTES
HOURS
LEAP YEAR
CALCULATION
DAYS
MONTHS
YEARS
C
WEEKDAY
013aaa092
Fig 8. Data flow for the time function
During read/write operations, the time counting circuits (memory locations 02h through
08h) are blocked.
This prevents
• Faulty reading of the clock and calendar during a carry condition
• Incrementing the time registers, during the read cycle
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 access is
serviced. A maximum of 1 request can be stored; therefore, all accesses must be
completed within 1 second (see Figure 9).
PCF8563
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© NXP B.V. 2012. All rights reserved.
Product data sheet
Rev. 10 — 3 April 2012
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