SM8578BV Nippon_Precision_Circuits America, SM8578BV Datasheet - Page 12

• Manufacturer Part Number: SM8578BV
• Description: Real-time Clock ic
• Manufacturer: Nippon_Precision_Circuits America

Setting the Alarm
Alarms can be set for day, weekday, hour and
minute. An alarm can also be set for more than one
weekday. Note that it is recommended that AF and
AIE be set to 0 to avoid accidental hardware inter-
rupts while setting the alarm.
After the alarm data is entered, initialization occurs
when AF is again set to 0. The alarm interrupt is
enabled by writing 1 to AIE.
If the hardware interrupt is not used, then AIE should
be set to 0. In this case, an alarm can still be con-
trolled by software monitoring of AF using read
cycles.
Example 1
To set an alarm for 6pm of the following day:
Monitoring Oscillator Frequency
• Set bits AIE and AF to 0.
C1
R1
R2
CG
SW
VSS
XT
VDD
XTN
CE
SM8578BV
INTN
Example 2
To set an alarm for 6am for Monday to Friday:
• Set the day register AE bit to 1 (don’t care).
• Acquire the current weekday setting from regis-
• Write 18
• Write 00
• Set AF to 0 and AIE to 1.
• Set bits AIE and AF to 0.
• Set the day register AE bit to 1 (don’t care).
• Write 3E
• Write 06
• Write 00
• Set AF to 0 and AIE to 1.
ter address 3, rotate result left by 1 bit, and
write to weekday alarm register (while monitor-
ing the fr bit).
R3
H
H
H
H
H
R1=R2 =10k
R3=10k
C1=0.1 F typ.)
to the hour alarm register.
to the minute alarm register.
to the hour alarm register.
to the minute alarm register.
to the weekday alarm register.
NIPPON PRECISION CIRCUITS—12
typ.)
INTN output (1Hz)
typ.)