m48t37v STMicroelectronics, m48t37v Datasheet - Page 14

• Manufacturer Part Number: m48t37v
• Description: 5.0 Or 3.3v, 256 Kbit 32 Kbit X 8 Timekeeper Sram
• Manufacturer: STMicroelectronics

3.4
Note:
14/29
Setting the alarm clock
Registers 7FF5h-7FF2h contain the alarm settings. The alarm can be configured to go off at
a predetermined time on a specific day of the month or repeat every day, hour, minute, or
second. It can also be programmed to go off while the M48T37Y/V is in the battery back-up
mode of operation to serve as a system wake-up call.
RPT1-RPT4 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 RPT1-RPT4, AF is set. If AFE is also set, the alarm condition activates the
IRQ/FT pin. To disable alarm, write '0' to the Alarm Date registers and RPT1-4. The alarm
flag and the IRQ/FT output are cleared by a READ to the Flags Register as shown in
Figure
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 the Alarm in Battery Back-up Mode Enable (ABE) and the 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 M48T37Y/V was in the deselect mode during
power-up.
Figure 7.
Table 6.
RPT4
1
1
1
1
0
7. A subsequent READ of the Flags Register is necessary to see that the value of the
A0-A14
ACTIVE FLAG BIT
IRQ/FT
Figure 8
Alarm interrupt reset waveform
Alarm repeat modes
illustrates the back-up mode alarm timing.
RPT3
1
1
1
0
0
RPT2
1
1
0
0
0
ADDRESS 7FF0h
15ns Min
RPT1
1
0
0
0
0
Table 6
Once per Second
shows the possible
Alarm Activated
Once per Minute
Once per Month
Once per Hour
Once per Day
AI01677B