m48t201v STMicroelectronics, m48t201v Datasheet - Page 18

• Manufacturer Part Number: m48t201v
• Description: 5.0 Or 3.3v Timekeeper Supervisor
• Manufacturer: STMicroelectronics

3.5
Note:
18/35
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 back-up to serve
as a system wake-up call.
Bits RPT5-RPT1 put the alarm in the repeat mode of operation.
configurations. Codes not listed in the table default to the once per second mode to quickly
alert the user of an incorrect alarm setting.
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
value of the Alarm Flag has been reset to '0.'
The IRQ/FT pin can also be activated in the battery 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 M48T201Y/V was in the deselect mode
during power-up.
Figure 7.
Table 6.
RPT5
1
1
1
1
1
0
A0-A18
ACTIVE FLAG BIT
IRQ/FT
Figure
Alarm interrupt reset waveforms
Alarm repeat modes
RPT4
1
1
1
1
0
0
7. A subsequent READ of the Flags Register is necessary to see that the
Figure 8 on page 19
RPT3
1
1
1
0
0
0
RPT2
illustrates the back-up mode alarm timing.
1
1
0
0
0
0
ADDRESS 7FFF0h
15ns Min
RPT1
1
0
0
0
0
0
Table 6
Once per Second
Once per Minute
Once per Month
Once per Hour
Alarm setting
Once per Year
Once per Day
HIGH-Z
shows the possible
AI02331