M48T201Y, M48T201V Clock operation
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If a battery low indication is generated during the 24-hour interval check, this indicates that
the battery is near end of life. However, data is not compromised due to the fact that a
nominal V
CC
is supplied. In order to insure data integrity during subsequent periods of
battery backup mode, the battery should be replaced. The SNAPHAT
®
top may be replaced
while V
CC
is applied to the device.
Note: This will cause the clock to lose time during the interval the battery/crystal is removed.
The M48T201Y/V only monitors the battery when a nominal V
CC
is applied to the device.
Thus applications which require extensive durations in the battery backup mode should be
powered-up periodically (at least once every few months) in order for this technique to be
beneficial. Additionally, if a battery low is indicated, data integrity should be verified upon
power-up via a checksum or other technique.
3.12 Initial power-on defaults
Upon application of power to the device, the following register bits are set to a '0' state:
WDS; BMB0-BMB4; RB0-RB1; AFE; ABE; SQWE; W; R; FT (see Ta bl e 9).
Table 9. Default values
Condition W R FT AFE ABE SQWE
Watchdog
register
(1)
1. WDS, BMB0-BMB4, RB0, RB1.
Initial power-up
(Battery attach for
SNAPHAT)
(2)
2. State of other control bits undefined.
000000 0
RESET
(3)
3. State of other control bits remains unchanged.
000000 0
Power-down
(4)
4. Assuming these bits set to '1' prior to power-down.
000111 0
