PCF8564A datasheet(10/44 Pages) NXP

10 / 44 page

PCF8564A_1

Product data sheet

Rev. 1 — 8 October 2009

10 of 44

NXP Semiconductors

PCF8564A

Real time clock and calendar

The VL ﬂag is intended to detect the situation when VDD is decreasing slowly, for example

under battery operation. Should the oscillator stop or VDD reach Vlow before power is

re-asserted, then the VL ﬂag will be set. This indicates that the time is possibly corrupted.

8.4.2 Register Minutes

8.4.3 Register Hours

8.4.4 Register Days

[1]

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

value which is exactly divisible by 4, including the year 00.

8.4.5 Register Weekdays

Table 10.

Minutes - minutes register (address 03h) bit description

Bit

Symbol

Value

Place value Description

unused

6 to 4 MINUTES

0 to 5

ten’s place

actual minutes coded in BCD format

3 to 0

0 to 9

unit place

Table 11.

Hours - hours register (address 04h) bit description

Bit

Symbol

Value

Place value Description

7 to 6 -

unused

5 to 4 HOURS

0 to 2

ten’s place

actual hours coded in BCD format

3 to 0

0 to 9

unit place

Table 12.

Days - days register (address 05h) bit description

Bit

Symbol

Value

Place value Description

7 to 6 -

unused

5to4 DAYS[1]

0 to 3

ten’s place

actual day coded in BCD format

3 to 0

0 to 9

unit place

Table 13.

Weekdays - weekdays register (address 06h) bit description

Bit

Symbol

Value

Description

7 to 3 -

unused

2 to 0 WEEKDAYS

0 to 6

actual weekday values, see Table 14

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