Datasheet

Figure 18. Crystal accuracy across temperature
–160
0 10 20 30 40 50 60 70
Frequency (ppm)
Temperature °C
80–10–20–30–40
–100
–120
–140
–40
–60
–80
20
0
–20
= –0.036 ppm/ °C
2
± 0.006 ppm/ °C
2
K
DF
= K x (T – T
O
)
2
F
T
O
= 25°C ± 5°C
Figure 19. Calibration waveform
NORMAL
POSITIVE
CALIBRATION
NEGATIVE
CALIBRATION
3.3
Setting alarm clock registers
Address locations 0Ah-0Eh contain the alarm settings. The alarm can be configured 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
RPT5–RPT1 put the alarm in the repeat mode of operation. Table 6. Alarm repeat modes shows the possible
configurations. 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 RPT5–RPT1,
the AF (alarm flag) is set. If AFE (alarm flag enable) is also set (M41T62/65), the alarm condition activates the
IRQ /OUT or IRQ /FT/OUT pin. To disable the alarm, write '0' to the alarm date register and to RPT5–RPT1.
Note: If the address pointer is allowed to increment to the flag register address, an alarm condition will not cause
the interrupt/flag to occur until the address pointer is moved to a different address. It should also be noted that if
the last address written is the “Alarm Seconds,” the address pointer will increment to the flag address, causing
this situation to occur.
The
IRQ output is cleared by a READ to the flags register as shown in Figure 20. Alarm interrupt reset waveform.
A subsequent READ of the flags register is necessary to see that the value of the alarm flag has been reset to '0.'
M41T62, M41T64, M41T65
Setting alarm clock registers
DS3840 - Rev 24
page 17/42