M41T62 datasheet(25/40 Pages) STMICROELECTRONICS

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M41T62/63/64/65

Clock operation

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3.3

Setting alarm clock registers

Address 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 RPT5–RPT1 put the alarm in the repeat

mode of operation. Table 7 on page 25 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 RPT5–RPT1, the AF (Alarm Flag) is set. If AFE (Alarm Flag Enable) is also set

(M41T62/65), the alarm condition activates the IRQ/OUT or IRQ/FT/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 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 “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 Register as shown in Figure 22 on

page 25. A subsequent READ of the Flags Register is necessary to see that the value of the

Alarm Flag has been reset to '0.'

Figure 22.

Alarm interrupt reset waveform

Table 7.

Alarm repeat modes

RPT5

RPT4

RPT3

RPT2

RPT1

Alarm setting

Once per second

Once per minute

Once per hour

Once per day

Once per month

Once per year

ALARM FLAG BIT (AF)

0Fh

0Eh

00h

HIGH-Z

AI08898

IRQ/OUT or

IRQ/FT/OUT

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