M41T50 datasheet(13/23 Pages) STMICROELECTRONICS

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M41T50

Setting Alarm Clock Registers

Address locations 0Ah-0Eh contain the alarm set-

tings. 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 RPT5–RPT1

put the alarm in the repeat mode of operation. Ta-

ble 3., page 13 shows the possible configurations.

Codes not listed in the table default to the once per

second mode to quickly alert the user of an incor-

rect alarm setting.

When the clock information matches the alarm

clock settings based on the match criteria defined

by RPT5–RPT1, the AF (Alarm Flag) is set. If AFE

(Alarm Flag Enable) is also set, the alarm condi-

tion activates the IRQ/OUT pin. To disable the

alarm, write '0' to the Alarm Date Register and to

RPT5–RPT1.

Note: If the address pointer is allowed to incre-

ment to the Flag Register address, an alarm con-

dition will not cause the Interrupt/Flag to occur until

the address pointer is moved to a different ad-

dress. It should also be noted that if the last ad-

dress written is the “Alarm Seconds,” the address

pointer will increment to the Flag address, causing

this situation to occur.

The IRQ output is cleared by a READ to the Flags

sequent READ of the Flags Register is necessary

to see that the value of the Alarm Flag has been

reset to '0.'

Figure 11. Alarm Interrupt Reset Waveform

Table 3. Alarm Repeat Modes

RPT5

RPT4

RPT3

RPT2

RPT1

Alarm Setting

Once per Second

Once per Minute

Once per Hour

000

Once per Day

Once per Month

000

Once per Year

ALARM FLAG BIT (AF)

0Fh

0Eh

00h

HIGH-Z

AI09113

IRQ/OUT

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