ISL12023 Ver la hoja de datos (PDF) - Renesas Electronics

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ISL12023

Low Power RTC with Battery-Backed SRAM and Embedded Temp Compensation ±5ppm with Auto Daylight Saving

Renesas Electronics 

ISL12023

DST Control Registers (DSTCR)

8 bytes of control registers have been assigned for the Daylight

Savings Time (DST) functions. DST beginning (set Forward) time

is controlled by the registers DstMoFd, DstDwFd, DstDtFd, and

DstHrFd. DST ending time (set Backward or Reverse) is controlled

by DstMoRv, DstDwRv, DstDtRv and DstHrRv.

Tables 22 and 23 describe the structure and functions of the DSTCR.

DST FORWARD REGISTERS (20H TO 23H)

DST forward is controlled by the following DST Registers:

DST Enable

DSTE is the DST Enabling Bit located in bit 7 of register 20h

(DstMoFdxx). Set DSTE = 1 will enable the DSTE function. Upon

powering up for the first time (including battery), the DSTE bit

defaults to “0”. When DSTE is set to “1” the RTC time must be at

least one hour before the scheduled DST time change for the

correction to take place. When DSTE is set to “0”, the DSTADJ bit

in the Status Register automatically resets to “0”.

DST Month Forward

DstMoFd sets the Month that DST starts. The format is the same

as for the RTC register month, from 1 to 12. The default value for

the DST begin month is 00h.

DST Day/Week Forward

DstDwFd contains both the Day of the Week and the Week of the

Month data for DST Forward control. DST can be controlled either

by actual date or by setting both the Week of the month and the

Day of the Week. DstDwFdE sets the priority of the Day/Week

over the Date. For DstDwFdE = 1, Day/Week is the priority. You

must have the correct Day of Week entered in the RTC registers

for the Day/Week correction to work properly.

• Bits 0, 1, 2 contain the Day of the week information which sets

the Day of the Week that DST starts. Note that Day of the week

counts from 0 to 6, like the RTC registers. The default for the

DST Forward Day of the Week is 00h (normally Sunday).

• Bits 3, 4, 5 contain the Week of the Month information that

sets the week that DST starts. The range is from 1 to 5, and

Week 7 is used to indicate the last week of the month. The

default for the DST Forward Week of the Month is 00h.

DST Date Forward

DstDtfd controls which Date DST begins. The format for the Date

is the same as for the RTC register, from 1 to 31. The default

value for DST forward date is 00h. DstDtFd is only effective if

DstDwFdE = 0.

DST Hour Forward

DstHrFd controls the hour that DST begins. The RTC hour and

DstHrFd registers have the same formats except there is no

Military bit for DST hour. The user sets the DST hour with the

same format as used for the RTC hour (AM/PM or MIL) but

without the MIL bit, and the DST will still advance as if the MIL bit

were there. The default value for DST hour Forward is 00h.

DST REVERSE REGISTERS (24H TO 27H)

DST end (reverse) is controlled by the following DST Registers:

DST Month Reverse

DstMoRv sets the Month that DST ends. The format is the same

as for the RTC register month, from 1 to 12. The default value for

the DST end month is October (10h).

DST Day/Week Reverse

DstDwRv contains both the Day of the Week and the Week of the

Month data for DST Reverse control. DST can be controlled either

by actual date or by setting both the Week of the month and the

Day of the Week. DstDwRvE sets the priority of the Day/Week

over the Date. For DstDwRvE = 1, Day/Week is the priority. You

must have the correct Day of Week entered in the RTC registers

for the Day/Week correction to work properly.

ADDRESS

20h

21h

22h

23h

FUNCTION

Month Forward

Day Forward

Date Forward

Hour Forward

7

DSTE

0

0

0

ADDRESS

NAME

7

24h

Month Reverse

0

25h

Day Reverse

0

26h

Date Reverse

0

27h

Hour Reverse

0

TABLE 22. DST FORWARD REGISTERS

6

5

4

3

0

0

MoFd20

MoFd13

DwFdE

WkFd12

WkFd11

WkFd10

0

DtFd21

DtFd20

DtFd13

0

HrFd21

HrFd20

HrFd13

TABLE 23. DST REVERSE REGISTERS

6

5

4

3

0

0

MoRv20

MoRv13

DwRvE

WkRv12

WkRv11

WkRv10

0

DtRv21

DtRv20

DtRv13

0

HrRv21

HrRv20

HrRv13

2

MoFd12

DwFd12

DtFd12

HrFd12

2

MoRv12

DwRv12

DtRv12

HrRv12

1

MoFd11

DwFd11

DtFd11

HrFd11

1

MoRv11

DwRv11

DtRv11

HrRv11

0

MoFd10

DwFd10

DtFd10

HrFd10

0

MoRv10

DwRv10

DtRv10

HrRv10

FN6682 Rev 3.00

December 6, 2011

Page 20 of 29

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