m48t201v STMicroelectronics, m48t201v Datasheet - Page 24

• Manufacturer Part Number: m48t201v
• Description: 5.0 Or 3.3v Timekeeper Supervisor
• Manufacturer: STMicroelectronics

Note:
3.12
24/35
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
battery back-up mode, the battery should be replaced. The SNAPHAT
while V
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
Thus applications which require extensive durations in the battery back-up 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.
Initial power-on defaults
Table 9.
1. WDS, BMB0-BMB4, RB0, RB1.
2. State of other control bits undefined.
3. State of other control bits remains unchanged.
4. Assuming these bits set to '1' prior to power-down.
Initial Power-up
(Battery Attach for
SNAPHAT)
Power-down
RESET
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
CC
(3)
Condition
CC
is applied to the device.
(2)
(4)
Default values
is supplied. In order to insure data integrity during subsequent periods of
W
0
0
0
R
0
0
0
FT
0
0
0
AFE
0
0
1
CC
ABE
0
0
1
is applied to the device.
®
SQWE
top may be replaced
Table
0
0
1
9).
Watchdog
register
0
0
0
(1)