Micro Crystal

Ultra Small Real Time Clock / Calendar Module

RV-4162

21/39

4.4. ALARM FUNCTION

Addresses locations 0Ah-0Eh contain the alarm settings. The alarm can be configured to go off at a prescribed

time on a specific month, date, hour, minute, or second, or repeat every year, month, day, hour, minute, or second.

Bits ARM5 - ARM1 put the alarm in the repeat mode of operation. The table below shows the possible

configurations. Codes not listed in the table default to the once per second mode to quickly alert the user of an

incorrect alarm setting.

When the clock information matches the alarm clock settings based on the match criteria defined by ARM5 -

ARM1, the AF (alarm flag) is set. If AFE (alarm flag enable) is also set, the alarm condition activates the INT pin 6.

To disable the alarm, write

“0” to the Date Alarm register and to ARM5 - ARM1.

Note: If the address pointer is allowed to increment to the flag register address, an alarm condition will not cause

the interrupt / flag to occur until the address pointer is moved to a different address. It should also be noted that if

the last address written is the Second Alarm, the address pointer will increment to the flag address, causing this

situation to occur.

The INT is cleared by a READ to the Flags register as shown in figure below. A subsequent READ of the Flags

register is necessary to see that the value of the alarm flag has been reset to

“0”.

Alarm interrupt reset waveform:

Alarm Repeat Mode Settings (addresses 0Bh to 0Eh, ARM5 to ARM

1…bits description)

Address

Function

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0Bh

Date Alarm

ARM4

ARM5

20

10

8

4

2

1

0Ch

Hour Alarm

ARM3

0

20

10

8

4

2

1

0Dh

Minute Alarm

ARM2

40

20

10

8

4

2

1

0Eh

Second Alarm

ARM1

40

20

10

8

4

2

1

ARM5

ARM4

ARM3

ARM2

ARM1

Alarm setting

1

1

1

1

1

Once per second

1

1

1

1

0

Once per minute

1

1

1

0

0

Once per hour

1

1

0

0

0

Once per day

1

0

0

0

0

Once per month

0

0

0

0

0

Once per year

INT