FN6690 datasheet(10/19 Pages) RENESAS

10 / 19 page

ISL12008 I2C Real Time Clock with Battery Backup

FN6690 Rev 1.00

Page 10 of 19

Sep 26, 2008

Real Time Clock Registers

Addresses [00h to 06h, and 1Fh]

RTC REGISTERS (SC, MN, HR, DW, DT, MO, YR, SS)

These registers depict BCD representations of the time. As

such, SC (Seconds, address 00h) and MN (Minutes, address

01h) range from 0 to 59, HR (Hour, address 02h) is in 24-hour

mode with a range from 0 to 23, DW (Day of the Week,

address 03h) is 1 to 7, DT (Date, address 04h) is 1 to 31, MO

(Month, address 05h) is 1 to 12, YR (Year, address 06h) is 0 to

99, and SS (Sub-Seconds/Hundredths of Seconds, address

1Fh) is 0 to 99. The default for all the time keeping bits are set

to “0” at power up.

Bit D7 of SC register contain the crystal enable/disable bit (ST).

Setting ST to “1” will disable the crystal from oscillating and

stop the counting in RTC register. When the ST bit is set to “1”,

it will casue the OF bit to set to “1” due to no crystal oscillation

on the X1 pin. The ST bit is set to “0” on power-up for normal

operation.

Bit D7 of MN register contain the Oscillator Fail Indicator bit

(OF). This bit is set to a “1” when the X1 pin has no oscillation.

This bit can be reset when the X1 has crystal oscillation and a

write to “0”. This bit can only be written as “0” and not as a “1”.

The OF bit is set to “1” at power-up from a complete power

down (VDD and VBAT are removed). Address 9, bit 7 is also

used as the OF bit for DS1340 compatibility, and the two OF

bits are interchangable.

Bits D6 and D7 of HR register (century/hours register) contain

the century enable bit (CEB) and the century bit (CB). Setting

CEB to a '1' will cause CB to toggle, either from '0' to '1' or from

'1' to '0' at the turn of the century (depending upon its initial

state). If CEB is set to a '0', CB will not toggle.

The DW register provides a Day of the Week status and uses

three bits DW2 to DW0 to represent the seven days of the week.

The counter advances in the cycle 1-2-3-4-5-6-7-1-2-…

The assignment of a numerical value to a specific day of the

week is arbitrary and may be decided by the system software

designer.

TABLE 1. REGISTER MEMORY MAP

ADDR. SECTION

REG

NAME

BIT

REG

RTC

RANGE DEFAULT

00h

RTC

SC22

SC21

SC20

SC13

SC12

SC11

SC10

0 to 59

00h

01h

MN22

MN21

MN20

MN13

MN12

MN11

MN10

0 to 59

80h

02h

CEB

HR21

HR20

HR13

HR12

HR11

HR10

0 to 23

00h

03h

00000

DW12

DW11

DW10

1 to 7

00h

04h

DT21

DT20

DT13

DT12

DT11

DT10

1 to 31

00h

05h

MO20

MO13

MO12

MO11

MO10

1 to 12

00h

06h

YR23

YR22

YR21

YR20

YR13

YR12

YR11

YR10

0 to 99

00h

07h

Control

DTR

OUT

DTR5

DTR4

DTR3

DTR2

DTR1

DTR0

N/A

80h

08h

INT

ALME

LPMODE

00000

N/A

00h

09h

0000000

N/A

80h

0Ah

ATR

BMATR1

BMATR0

ATR5

ATR4

ATR3

ATR2

ATR1

ATR0

N/A

00h

0Bh

Status

ARST

XSTOP

RESEAL

ALM

BAT

RTCF

N/A

03h

0Ch

Alarm0

SCA

ESCA

ASC22

ASC21

ASC20

ASC13

ASC12

ASC11

ASC10

00 to 59

00h

0Dh

MNA

EMNA

AMN22

AMN21

AMN20

AMN13

AMN12

AMN11

AMN10

00 to 59

00h

0Eh

HRA

EHRA

AHR21

AHR20

AHR13

AHR12

AHR11

AHR10

0 to 23

00h

0Fh

DTA

EDTA

ADT21

ADT20

ADT13

ADT12

ADT11

ADT10

1 to 31

00h

10h

MOA

EMOA

AMO20

AMO13

AMO12

AMO11

AMO10

1 to 12

00h

11h

DWA

EDWA

0000

ADW12

ADW11

ADW10

1 to 7

00h

1Fh

(Read-

Only)

RTC

SS23

SS22

SS21

SS20

SS13

SS12

SS11

SS10

0 to 99

00h

NOTE: 0 = must be set to‘0’

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