M48T201V-70MH1 STMICROELECTRONICS [STMicroelectronics], M48T201V-70MH1 Datasheet - Page 22

• Manufacturer Part Number: M48T201V-70MH1
• Description: 3.3V-5V TIMEKEEPER CONTROLLER
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M48T201Y, M48T201V
Battery Low Warning
The M48T201Y/V automatically performs battery
voltage monitoring upon power-up and at factory-
programmed time intervals of approximately 24
hours. The Battery Low (BL) Bit, Bit D4 of Flags
Register 7FFF0h, will be asserted if the battery
voltage is found to be less than approximately
2.5V. The BL Bit will remain asserted until comple-
tion of battery replacement and subsequent bat-
tery low monitoring tests, either during the next
power-up sequence or the next scheduled 24-hour
interval.
If a battery low is generated during a power-up se-
quence, this indicates that the battery is below ap-
proximately 2.5V and may not be able to maintain
data integrity in the SRAM. Data should be consid-
ered suspect and verified as correct. A fresh bat-
tery should be installed.
If a battery low indication is generated during the
24-hour interval check, this indicates that the bat-
tery is near end of life. However, data is not com-
promised due to the fact that a nominal V
supplied. In order to insure data integrity during
Table 9. Default Values
Note: 1. WDS, BMB0-BMB4, RB0, RB1.
22/33
Initial Power-up
(Battery Attach for SNAPHAT)
Power-down
RESET
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.
(3)
(4)
Condition
(2)
W
0
0
0
CC
R
0
0
0
is
subsequent periods of battery back-up mode, the
battery should be replaced. The SNAPHAT
may be replaced while V
vice.
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
cations which require extensive durations in the
battery back-up mode should be powered-up peri-
odically (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
Upon application of power to the device, the fol-
lowing register bits are set to a '0' state: WDS;
BMB0-BMB4; RB0-RB1; AFE; ABE; SQWE; W; R;
FT (see Table 9).
FT
0
0
0
AFE
CC
0
0
1
is applied to the device. Thus appli-
ABE
0
0
1
CC
SQWE
is applied to the de-
0
0
1
WATCHDOG
Register
0
0
0
®
(1)
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