PCF8564A_10 datasheet(9/45 Pages) NXP

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PCF8564A

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Product data sheet

Rev. 02 — 30 September 2010

9 of 45

NXP Semiconductors

PCF8564A

Real time clock and calendar

8.4 Time and date registers

The majority of the registers are coded in the BCD format to simplify application use.

8.4.1 Register Seconds

[1]

Start-up value.

8.4.1.1

Voltage low detector and clock monitor

The PCF8564A has an on-chip voltage low detector. When VDD drops below Vlow the VL

(Voltage Low) flag is set to indicate that the integrity of the clock information is no longer

guaranteed. The VL flag can only be cleared by using the interface.

Table 8.

Seconds - seconds and clock integrity status register (address 02h) bit

description

Bit

Symbol

Value

Place value Description

clock integrity is guaranteed

1[1]

integrity of the clock information is not guaranteed

6 to 4 SECONDS 0 to 5

ten’s place

actual seconds coded in BCD format, see Table 9

3 to 0

0 to 9

unit place

Table 9.

Seconds coded in BCD format

Seconds value in

decimal

Upper-digit (ten’s place)

Digit (unit place)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

000

0000

000

0001

000

0010

000

1001

001

0000

101

1000

101

1001

Fig 5.

Voltage low detection

VL set

normal power

operation

period of battery

operation

VDD

Vlow

mgr887

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