PC8564A-1 Ver la hoja de datos (PDF) - NXP Semiconductors.

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PC8564A-1

Real time clock and calendar

NXP Semiconductors. 

NXP Semiconductors

PCF8564A

Real time clock and calendar

8.4.7 Register Years

Table 18. Years - years register (08h) bit description

Bit Symbol

Value Place value Description

7 to 4 YEARS

0 to 9

ten’s place actual year coded in BCD format[1]

3 to 0

0 to 9

unit place

[1] When the register Years overflows from 99 to 00, the century bit C in the register Months is toggled.

The PCF8564A compensates for leap years by adding a 29th day to February if the year

counter contains a value which is divisible by 4, including the year 00.

8.5 Setting and reading the time

Figure 5 shows the data flow and data dependencies starting from the 1 Hz clock tick.

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Fig 5. Data flow for the time function

During read/write operations, the time counting circuits (memory locations 02h through

08h) are blocked.

This prevents

• Faulty writing or 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 6).

PCF8564A

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 3 — 26 August 2013

© NXP B.V. 2013. All rights reserved.

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