M48T201Y, M48T201V

Clock operation

19/37

3.5

Setting the alarm clock

Registers 7FFF6h-7FFF2h contain the alarm settings. The alarm can be configured to go off

at a prescribed time on a specific month, day of month, hour, minute, or second or repeat

every month, day of month, hour, minute, or second.

It can also be programmed to go off while the M48T201Y/V is in the battery backup to serve

as a system wake-up call.

Bits RPT5-RPT1 put the alarm in the repeat mode of operation. Table 6 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.

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

register and RPT1-5. The IRQ/FT output is cleared by a READ to the flags register as

shown in Figure 7. A subsequent 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 battery backup mode. The IRQ/FT will go low if

an alarm occurs and both ABE (alarm in battery backup 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 M48T201Y/V was in the deselect mode during power-up.

Figure 8 on page 20 illustrates the backup mode alarm timing.

Figure 7.

Alarm interrupt reset waveforms

Table 6.

Alarm repeat modes

RPT5

RPT4

RPT3

RPT2

RPT1

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

AI02331

A0-A18

ACTIVE FLAG BIT

ADDRESS 7FFF0h

IRQ/FT

15ns Min

HIGH-Z