PCF2123TS datasheet(13/55 Pages) NXP

13 / 55 page

PCF2123_2

Product data sheet

Rev. 02 — 4 December 2009

13 of 55

NXP Semiconductors

PCF2123

SPI Real time clock/calendar

9.6 Time and date function

The majority of the registers are coded in the Binary Coded Decimal (BCD) format. BCD

is used to simplify application use. An example is shown for the seconds in Table 9.

9.6.1 Register Seconds

[1]

Default value.

9.6.2 Register Minutes

9.6.3 Register Hours

Table 8.

Seconds - seconds register (address 02h) bit description

Bit

Symbol

Value

Place value Description

clock integrity is guaranteed

1[1]

clock integrity is not guaranteed; oscillator has

stopped or been interrupted

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

(decimal)

Upper-digit (ten’s place)

Digit (unit place)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

00000000

00000001

00000010

::::::::

00001001

00010000

::::::::

01011000

01011001

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

12 hour mode[1]

AMPM

indicates AM

indicates PM

HOURS

0 to 1

ten’s place

actual hours in 12 hour mode coded in BCD format

3 to 0

0 to 9

unit place

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