ISL12022M_10 Datasheet, PDF (22/31 Pages) Intersil Corporation – Low Power RTC with Battery Backed SRAM,Integrated ±5ppm Temperature Compensation and Auto Daylight Saving

ISL12022M
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.
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).
ADDRESS FUNCTION
20h
Month
Forward
21h
Day Forward
22h
Date
Forward
23h
Hour
Forward
7
DSTE
0
0
0
TABLE 20. DST FORWARD REGISTERS
6
5
4
3
0
0
MoFd20 MoFd13
DwFdE
0
WkFd12
DtFd21
WkFd11
DtFd20
WkFd10
DtFd13
0
HrFd21
HrFd20
HrFd13
2
MoFd12
DwFd12
DtFd12
HrFd12
1
MoFd11
0
MoFd10
DwFd11
DtFd11
DwFd10
DtFd10
HrFd11 HrFd10
ADDRESS
NAME
7
Month
0
24h
Reverse
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
2
MoRv12
1
MoRv11
0
MoRv10
DwRvE
0
0
WkRv12
DtRv21
HrRv21
WkRv11
DtRv20
HrRv20
WkRv10
DtRv13
HrRv13
DwRv12
DtRv12
HrRv12
DwRv11
DtRv11
HrRv11
DwRv10
DtRv10
HrRv10
22
FN6668.7
June 4, 2010