Rainbow Electronics DS1677 User Manual
Page 5
DS1677
5 of 17
DS1677 ADDRESS MAP Figure 3
BIT7
BIT0
00
0
10 SECONDS
SECONDS
01
0
10 MINUTES
MINUTES
02
0
12
24
10 HR
A/P
10 HR
HOURS
03
0
0
0
0
0
DAY
04
0
0
10 DATE
DATE
05
0
0
0
10 MO.
MONTH
06
10 YEAR
YEAR
07
M
10 SEC ALARM
SECONDS ALARM
08
M
10 MIN ALARM
MINUTES ALARM
09
M
12
24
10 HR
A/P
10 HR
HOUR ALARM
0A
M
0
0
0
DAY ALARM
0B
CONTROL REGISTER
0C
STATUS REGISTER
0D
WATCHDOG REGISTER
0E
ADC REGISTER
0F
7F
RESERVED
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 zero. These bits will always read zero regardless of how they are written. Also
note that registers 0Fh to 7Fh are reserved. These registers will always read zero regardless of how they
are written. The contents of the time, calendar, and alarm registers are in the Binary–Coded Decimal
(BCD) format.
The DS1677 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 one being PM. In the 24–hour mode, bit 5 is the second 10–hour bit (20–23
hours).
The DS1677 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 one. An alarm will be generated every hour when the day and hour alarm
mask bits are set to one. Similarly, an alarm will be generated every minute when the day, hour, and
minute alarm mask bits are set to one. When day, hour, minute, and seconds alarm mask bits are set to
one, an alarm will occur every second.