M41TC8025AMC7F datasheet(26/41 Pages) STMICROELECTRONICS

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Operation

M41TC8025

26/41

DocID022873 Rev 4

is that in register 03h, only one bit should be set since that bit represents one day in a week

in the calendar while in register 0Ah, multiple bits can be set to represent the alarm for more

than one day in a week.

In the alarm date register in 0Ah, possible values are given in BCD format of "00", "01", "02",

and up to "31".

The AF bit in register 0Eh is the alarm flag. Once the alarm event occurs, the AF bit is set to

1. Once AF=1, it will not be auto-cleared and relies on the user to reset to 0. Resetting the

AF bit to 0 will release the IRQ pin from low to Hi-Z immediately.

The AIE bit in register 0Fh is the alarm enable bit. If the alarm is enabled (AIE=1) and there

is an alarm event, the IRQ pin will be pulled low. If the alarm is disabled (AIE=0), even if

there is an alarm event, the IRQ pin will remain Hi-Z. Setting the AIE bit to 0 while the IRQ

pin is low will immediately release the IRQ pin from low to Hi-Z.

Since RESET=1 will stop the clock chain below 4,096 Hz, the alarm interrupt will be

stopped.

2.8.2

Alarm interrupt example

Table 20 below gives the example of the alarm settings when "Day-of-week" has been

selected (WADA=0).

Note:

x means don't care.

If all the AM_M, AM_H and AM_D bits in register 08h, 09h and 0Ah are set to 1, that means

all the day-of-week, hours and minutes registers do not compare and the alarm will be

generated every minute.

Table 21 gives the example of the alarm settings when "Date (day of month)" has been

specified (WADA=1).

Table 20. Day-of-week alarm settings

Reg.

09h

Reg.

08h

Alarm description

Day-of-week alarm

Hour

alarm

Minute

alarm

Bit 7

AM_D

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Day-of-

week

is selected

(WADA=0)

1110

08h

80h~

FFh

Monday through Friday

at 8:00 am

0001

80h~

FFh

38h

Every Saturday and

Sunday at 38 minutes

each hour. Hour value is

not compared.

1111

18h

Every day at 6:18 pm

xxx

80h~

FFh

80h~

FFh

Alarm at every minute

Obsolete

Product(s)

- Obsolete

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