M48T212Y datasheet(16/32 Pages) STMICROELECTRONICS

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M48T212Y, M48T212V

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Setting the Alarm Clock

Address locations 6h-2h 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. It can also be pro-

grammed to go off while the M48T212Y/V is in the

battery back-up to serve as a system wake-up call.

Bits RPT5-RPT1 put the alarm in the repeat mode

of operation. Table 8 shows the possible configu-

rations. Codes not listed in the table default to the

once per second mode to quickly alert the user of

an incorrect alarm setting.

Note: User must transition address (or toggle chip

enable) to see Flag Bit change.

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

condition activates the IRQ/FT pin. To disable

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

RPT1-5. The IRQ/FT output is cleared by a READ

to the Flags Register as shown in Figure 8. A sub-

sequent READ of the Flags Register is necessary

to see that the value of the Alarm Flag has been

reset to '0.'

The IRQ/FT pin can also be activated in the bat-

tery back-up mode. The IRQ/FT will go low if an

alarm occurs and both ABE (Alarm in Battery

Back-up Mode Enable) and AFE are set. The ABE

and AFE Bits are reset during power-up, therefore

an alarm generated during power-up will only set

AF. The user can read the Flag Register at system

boot-up to determine if an alarm was generated

while the M48T212Y/V was in the deselect mode

during power-up. Figure 9., page 17 illustrates the

back-up mode alarm timing.

Figure 8. Alarm Interrupt Reset Waveforms

Table 8. Alarm Repeat Modes

RPT5

RPT4

RPT3

RPT2

RPT1

Alarm Setting

1111

Once per Second

1111

Once per Minute

1110

Once per Hour

1100

Once per Day

1000

Once per Month

0000

Once per Year

AI03021

A0-A3

ACTIVE FLAG BIT

ADDRESS 0h

IRQ/FT

HIGH-Z

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