M48T201V datasheet(24/35 Pages) STMICROELECTRONICS

24 / 35 page

Clock operation

M48T201Y, M48T201V

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 VCC is supplied. In order to insure data integrity during subsequent periods of

battery back-up mode, the battery should be replaced. The SNAPHAT® top may be replaced

while VCC 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 VCC is applied to the device.

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.

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 Table 9).

Table 9.

Default values

Condition

AFE

ABE

SQWE

Watchdog

WDS, BMB0-BMB4, RB0, RB1.

Initial Power-up

(Battery Attach for

SNAPHAT)(2)

State of other control bits undefined.

000

RESET(3)

State of other control bits remains unchanged.

000

Power-down(4)

Assuming these bits set to '1' prior to power-down.

000

111

M48T201V Datasheet(PDF) 24 Page - STMicroelectronics