DS1673 Datasheet, PDF (5/18 Pages) Dallas Semiconductor – Portable System Controller

DS1673 ADDRESS MAP Figure 3
DS1673
CLOCK, CALENDAR, AND ALARM
The time and calendar information is accessed by reading/writing the appropriate register bytes. Note that
some bits are set to 0. These bits will always read 0 regardless of how they are written. Also note that
registers 0Fh to 7Fh are reserved. These registers will always read 0 regardless of how they are written.
The contents of the time, calendar, and alarm registers are in the Binary-Coded Decimal (BCD) format.
The DS1673 can run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the 12- or
24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is the
AM/PM bit with logic 1 being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20-23 hours).
The DS1673 also contains a time of day alarm. The alarm registers are located in registers 07h to 0Ah.
Bit 7 of each of the alarm registers are mask bits (see Table 1). When all of the mask bits are logic 0, an
alarm will occur once per week when the values stored in timekeeping registers 00h to 03h match the
values stored in the time of day alarm registers. An alarm will be generated every day when mask bit of
the day alarm register is set to 1. An alarm will be generated every hour when the day and hour alarm
mask bits are set to 1. Similarly, an alarm will be generated every minute when the day, hour, and minute
alarm mask bits are set to 1. When day, hour, minute, and seconds alarm mask bits are set to 1, an alarm
will occur every second.
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