m48t129v STMicroelectronics, m48t129v Datasheet - Page 17

• Manufacturer Part Number: m48t129v
• Description: 5.0 Or 3.3v, 1 Mbit 128 Kbit X 8 Timekeeper Sram
• Manufacturer: STMicroelectronics

Setting the Alarm Clock
Registers 1FFF6h-1FFF2h 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 month, day,
hour, minute, or second. It can also be pro-
grammed to go off while the M48T129Y/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.
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 condi-
Figure 12. Alarm Interrupt Reset Waveform
Table 6. Alarm Repeat Mode
RPT5
1
1
1
1
1
0
AD0-AD7
ACTIVE FLAG BIT
IRQ/FT
Table 6., page 17
RPT4
1
1
1
1
0
0
shows the possible
RPT3
1
1
1
0
0
0
ADDRESS 1FF0h
15ns Min
tion 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
quent READ of the Flags Register is necessary to
see that the value of the Alarm Flag has been re-
set 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 M48T129Y/V was in the deselect mode
during power-up.
the back-up mode alarm timing.
RPT2
1
1
0
0
0
0
RPT1
Figure 13., page 18
1
0
0
0
0
0
HIGH-Z
M48T129Y, M48T129V
AI02581
Figure 12.
Once per Second
Alarm Activated
Once per Minute
Once per Month
Once per Hour
Once per Year
Once per Day
illustrates
A subse-
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