DS1921G-F5N MAXIM [Maxim Integrated Products], DS1921G-F5N Datasheet - Page 12

• Manufacturer Part Number: DS1921G-F5N
• Description: Thermochron iButton
• Manufacturer: MAXIM [Maxim Integrated Products]

Thermochron iButton
The DS1921G also contains an RTC alarm function. The
RTC Alarm registers are located in registers 0207h to
020Ah. The most significant bit of each of the alarm
registers is a mask bit. When all the mask bits are logic
0, an alarm occurs once per week when the values
stored in timekeeping registers 0200h to 0203h match
12
ADDRESS
020Ah
0200h
0201h
0202h
0203h
0204h
0205h
0206h
0207h
0208h
0209h
MS
______________________________________________________________________________________
1
0
0
0
0
ALARM REGISTER MASK BITS
(BIT 7 OF 0207h TO 20Ah)
CENT
BIT 7
MM
MM
MH
MD
MS
1
1
0
0
0
0
0
0
0
0
MH
BIT 6
12/24
12/24
1
1
1
0
0
0
0
0
0
10 Years
10 Seconds Alarm
10 Minutes Alarm
10 Seconds
10 Minutes
RTC Alarms
20 Hour
20 Hour
MD
AM/PM
AM/PM
Alarm
BIT 5
1
1
1
1
0
0
0
0
10 Date
Alarm once per second.
Alarm when seconds match (once per minute).
Alarm when minutes and seconds match (once every hour).
Alarm when hours, minutes, and seconds match (once every day).
Alarm when day, hours, minutes, and seconds match (once every week).
10 Months
10 Hour
10 Hour
Alarm
BIT 4
0
0
the values stored in the RTC Alarm registers. Any alarm
sets the timer alarm flag (TAF) in the device’s Status
register (address 214h). The bus master can set the
search conditions in the Control register (address
20Eh) to identify devices with timer alarms by means of
the conditional search function (see the ROM Function
Commands section).
BIT 3
0
0
RTC and RTC Alarm Registers Map
FUNCTION
Single Seconds Alarm
Single Minutes Alarm
BIT 2
Single Hours Alarm
Single Seconds
Single Minutes
Single Months
Single Hours
Single Years
Single Date
Day of Week Alarm
Day of Week
RTC Alarm Control
BIT 1
BIT 0