DS17885 Dallas, DS17885 Datasheet - Page 8

• Manufacturer Part Number: DS17885
• Description: (DS17886 / DS17887) 3V/5V Real-Time Clock
• Manufacturer: Dallas

The three time alarm bytes can be used in two ways. First, when the alarm time is written in the
appropriate hours, minutes, and seconds alarm locations, the alarm interrupt is initiated at the specified
time each day if the alarm enable bit is high. The second use condition is to insert a “don’t care” state in
one or more of the three time alarm bytes. The “don’t care” code is any hexadecimal value from C0 to
FF. The two most significant bits of each byte set the “don’t care” condition when at logic 1. An alarm is
generated each hour when the “don’t care” bits are set in the hours byte. Similarly, an alarm is generated
every minute with “don’t care” codes in the hours and minute alarm bytes. The “don’t care” codes in all
three time alarm bytes create an interrupt every second. The three time-alarm bytes can be used with the
date alarm as described in Wake-Up/Kickstart. The century counter is discussed later in this text.
Table 1. TIME, CALENDAR, AND ALARM DATA MODES
BANK 1, 48H
BANK 1, 49H
LOCATION
ADDRESS
OOH
01H
02H
03H
04H
05H
06H
07H
08H
09H
Seconds
Seconds Alarm
Minutes
Minutes Alarm
Hours 12-hour Mode
Hours 24-hour Mode
Hours Alarm 12-hour Mode
Hours Alarm 24-hour Mode
Days of the Week Sunday = 1
Date of Month
Month
Year
Century
Date Alarm
FUNCTION
DECIMAL
RANGE
0 to 59
0 to 59
0 to 59
0 to 59
1 to 12
0 to 23
1 to 12
0 to 23
1 to 31
1 to 12
0 to 99
0 to 99
1 to 31
1 to 7
8 of 38
01 to 0C AM, 81 to 8C PM
01 to 0C AM, 81 to 8C PM
BINARY DATA MODE
01 to 0C
00 to 3B
00 to 3B
00 to 3B
00 to 17
00 to 17
01 to 07
01 to 1F
00 to 63
00 to 63
01 to 1F
00 to B
RANGE
01 to 12 AM, 81 to 92 PM
01 to 12 AM, 81 to 92 PM
BCD DATA MODE
00 to 59
00 to 59
00 to 59
00 to 59
00 to 23
00 to 23
01 to 07
01 to 31
01 to 12
00 to 99
00 to 99
01 to 31