BU9873 Datasheet, PDF (19/40 Pages) Rohm – I2C BUS Serial Interface RTC with High-precision Oscillation Adjustment

BU9873
Datasheet
5. Alarm Interrupt Function
The BU9873 has an alarm function that outputs an interrupt signal from INTRB pin to CPU when the day of the week, hour or
minute match with the preset time. There are two systems of alarms (Alarm_A, Alarm_B), and each may output interrupt
signal separately at a specified time. The alarm may be selectable between on and off for each day of the week, thus
allowing outputting alarm everyday or on a specific day of the week. Polling is possible for each alarm function
5-1. Usage of Alarm Interrupt Function
Users can set the time to generate an alarm interrupt. There are two systems of alarms, Alarm_A register (internal address
8h to Ah), Alarm_B register (internal address Bh to Dh), covering the day of the week, hour and minute.
Because Alarm_A and Alarm_B are the same function, only Alarm_A is explained as example.
Internal address
A3 A2 A1 A3
81 0 0 0
91 0 0 1
A1 0 1 0
Contents
D7
Alarm_A
(Minute Register)
—
Alarm_A
(Hour Register)
—
Alarm_A
(Day-of-week —
Register)
D6
AM₄₀
—
AW₆
D5
AM₂₀
AH₂₀
AP/AB
Data
D4
D3
AM₁₀ AM₈
AH₁₀ AH₈
AW₅
AW₄ AW₃
D2
AM₄
AH₄
AW₂
D1
AM₂
AH₂
AW₁
D0
AM₁
AH₁
AW₀
Alarm_A, Alarm_B hour register D5 is set to for PM in the 12-hour display system at AP/AB. The register D5 indicates 10
digit of hour digit in 24-hour display system at AH20.
To activate alarm operation, any imaginary alarm time setting should not be left to avoid un-matching.
AW0 to AW6 correspond to the day-of-the-week counter (W4, W2, W1) being set at (0, 0, 0) to (1, 1, 0).
No alarm pulses are output when all of AW0 to AW6 are set to 0.
Example of alarm time settings
Alarm Time Settings
Sun
AW0
Mon
AW1
Day-of-the-week
Tue Wed Thu
AW2 AW3 AW4
Fri
AW5
Sat
AW6
12-hour svstem
10
1
10
1
hour hour min min
24-hour system
10
1
10
1
hour hour min min
0:00AM every day
1
1
1
1
1
1
1
1
2
0
0
0
0
0
0
1:30AM every day
1
1
1
1
1
1
1
0
1
3
0
0
1
3
0
11:59AM every day
1
1
1
1
1
1
1
1
1
5
9
1
1
5
9
00:00PM on Monday
through Friday
0
1
1
1
1
1
1
3
2
0
0
1
2
0
0
1:30PM on Sunday
1
0
0
0
0
0
0
2
1
3
0
1
3
3
0
11:59PM Monday
Wednesday,and Friday
0
1
0
1
0
1
0
3
1
5
9
2
3
5
9
Designation of day-of-the-week and AW0 to AW6 in the above table is an example.
The alarm interruption is enabled only when the AALE, BALE bits are set to “1” (internal address Eh).
Alarm_A, Alarm_B enable bits
AALE, BALE
Description
0
Alarm_A (Alarm_B) Correspondence action invalid
1
Alarm_A (Alarm_B) Correspondence action valid
Default
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