ISL12023 Datasheet, PDF (20/28 Pages) Intersil Corporation – Low Power RTC with Battery-Backed SRAM and Embedded Temp Compensation ±5ppm with Auto Daylight Saving

ISL12023
events is retained). Set CLRTS = 1 to clear this register (add
09h, PWR_V_DD register).
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 20 and 21 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.
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 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,
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).
TABLE 20. DST FORWARD REGISTERS
ADDRESS FUNCTION
7
6
5
4
3
2
1
0
20h
Month Forward DSTE
0
0
MoFd20
MoFd13
MoFd12
MoFd11
MoFd10
21h
Day Forward
0
DwFdE
WkFd12
WkFd11
WkFd10
DwFd12
DwFd11
DwFd10
22h
Date Forward
0
0
DtFd21
DtFd20
DtFd13
DtFd12
DtFd11
DtFd10
23h
Hour Forward
0
0
HrFd21
HrFd20
HrFd13
HrFd12
HrFd11
HrFd10
ADDRESS
NAME
7
24h
Month Reverse
0
25h
Day Reverse
0
26h
Date Reverse
0
27h
Hour Reverse
0
TABLE 21. DST REVERSE REGISTERS
6
5
4
3
0
0
MoRv20
MoRv13
DwRvE
WkRv12
WkRv11
WkRv10
0
DtRv21
DtRv20
DtRv13
0
HrRv21
HrRv20
HrRv13
2
MoRv12
DwRv12
DtRv12
HrRv12
1
MoRv11
DwRv11
DtRv11
HrRv11
0
MoRv10
DwRv10
DtRv10
HrRv10
20
FN6682.2
June 24, 2009