Datasheet
PCF8523 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6 — 17 September 2013 23 of 78
NXP Semiconductors
PCF8523
Real-Time Clock (RTC) and calendar
8.6.7 Register Years
8.6.8 Data flow of the time function
Figure 13 shows the data flow and data dependencies starting from the 1 Hz clock tick.
During read/write operations, the time counting circuits (memory locations 03h through
09h) are blocked.
The blocking prevents:
• Faulty reading of the clock and calendar during a carry condition
• Incrementing the time registers during the read cycle
After the 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 one request can be stored; therefore, all accesses must be
completed within 1 second (see Figure 14
).
Table 21. Years - years register (09h) bit description
Bit Symbol Value Place value Description
7 to 4 YEARS 0 to 9 ten’s place actual year coded in BCD format
3to0 0to9 unit place
Fig 13. Data flow diagram of the time function
Fig 14. Access time for read/write operations
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