m41t93 STMicroelectronics, m41t93 Datasheet - Page 27

• Manufacturer Part Number: m41t93
• Description: Serial Spi Bus Rtc With Battery Switchover
• Manufacturer: STMicroelectronics

Note:
3.5
Note:
Figure 13. Crystal isolation example
The substrate pad should be tied to V
Setting the alarm clock registers
Address locations 0Ah-0Eh (Alarm 1) and 14h-18h (Alarm 2) contain the alarm settings.
Either alarm can be configured independently 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. Bits RPT15–RPT11 and RPT25-RPT21 put the alarms in the repeat mode of
operation.
Codes not listed in the table default to the once-per-second mode to quickly alert the user of
an incorrect alarm setting. When the clock information matches the alarm clock settings
based on the match criteria defined by RPT15–RPT11 and/or RPT25-RPT21, AF1 (Alarm 1
Flag) or AF2 (Alarm 2 Flag) is set. If A1IE (Alarm 1 Interrupt Enable) is set, the alarm
condition activates the IRQ/FT/OUT output pin. To disable either of the alarms, write a '0' to
the Alarm Date Registers and to the RPTx5–RPTx1 Bits.
If the address pointer is allowed to increment to the Flag Register address, or the last
address written is “Alarm Seconds,” the address pointer will increment to the Flag address,
and an alarm condition will not cause the Interrupt/Flag to occur until the address pointer is
moved to a different address.
The IRQ output is cleared by a READ to the Flags Register (0Fh) as shown in
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/OUT pin can also be activated in the battery back-up mode (see
page
28).
Table 6 on page 28
shows the possible bit configurations.
SS
.
Crystal
XI XO
V SS
Local Grounding
Plane (Layer 2)
AI11814
Figure 15 on
Figure
14. A
27/51