Datasheet

M41ST87Y, M41ST87W Clock operation
Doc ID 9497 Rev 10 33/54
Figure 22. Crystal accuracy across temperature
Figure 23. Calibration waveform
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. It can also be programmed to go off while the
M41ST87Y/W 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. Table 8 on page 34 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, the
AI07888
–160
0 10203040506070
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
= K x (T – T
O
)
2
F
T
O
= 25°C ± 5°C
AI00594B
NORMAL
POSITIVE
CALIBRATION
NEGATIVE
CALIBRATION