ISL12020MIRZ-T7A Datasheet, PDF (30/34 Pages) Intersil Corporation – Low Power RTC with Battery Backed SRAM, Integrated ±5ppm Temperature Compensation and Auto Daylight Saving

ISL12020M
The Enable bit (DSTE) is in the Month forward register, so the BCD
value for that register is altered with the additional bit. The Week
and Day values along with Week/Day vs Date select bit is in the
Week/Day register, so that value is also not straight BCD. Hour
and Month are normal BCD, but the Hour doesn’t use the MIL bit
since Military time PM values are already discretely different
from AM/PM time PM values. The DST reverse setting utilizes the
option to select the last week of the month for October, which
could have 4 or 5 weeks but needs to have the time change on
the last Sunday.
Note that the DSTADJ bit in the status register monitors whether
the DST forward adjustment has happened. When it is “1”, DST
forward has taken place. When it is “0”, then either DST reverse
has happened, or it has been reset either by initial power-up or if
the DSTE bit has been set to “0”.
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FN6667.5
December 13, 2011