Clock operations
Figure 8. Crystal accuracy across temperature
ppm
20
M48T58, M48T58Y
0
-20
-40
-60
ΔF
F
= -0.038
ppm
C2
(T - T0)2 ± 10%
T0 = 25 °C
-80
-100
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 °C
AI02124
Figure 9. Clock calibration
NORMAL
POSITIVE
CALIBRATION
NEGATIVE
CALIBRATION
AI00594B
6.5
Battery low flag
The M48T58/Y automatically performs periodic battery voltage monitoring upon power-up.
The Battery Low flag (BL), Bit D6 of the flags Register 1FFDh, will be asserted high if the
internal or SNAPHAT® battery is found to be less than approximately 2.5V and the Battery
Low Enable (BLE) Bit has been previously set to '1.' The BL flag will remain active until
completion of battery replacement and subsequent battery low monitoring tests.
If a battery low is generated during a power-up sequence, this indicates that the battery
voltage is below 2.5V (approximately), which may be insufficient to maintain data integrity.
Data should be considered suspect and verified as correct. A fresh battery should be
installed.
The SNAPHAT top may be replaced while VCC is applied to the device.
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