M41T82 datasheet(44/61 Pages) STMICROELECTRONICS

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Clock operation

M41T82-M41T83

44/61

Doc ID 12578 Rev 12

3.15

FT/RST pin, frequency test and reset output pin (M41T82

only)

On the M41T82, the 512 Hz frequency test signal and the reset output share the same pin,

FT/RST. When the FT bit (bit 6 of register 08h) is a 1, the 512 Hz test signal is activated on

the pin. With FT a 0 and VCC good (above VRST), the output will be high. If the 512 Hz is

enabled when VCC fails, the FT bit will be cleared and the output will go low to assert reset.

At power-up, FT will be 0 leaving the pin functioning as the reset output.

3.16

Initial power-on defaults

Upon initial application of power to the device, the register bits will initially power-on in the

state indicated in Table 17 and Table 18.

Table 17.

Initial power-on default values (part 1)

Condition(1)

All other control bits power-up in an undetermined state.

ST CB1 CB0 OUT FT

DCS

ACS

Digital

calib.

Analog

calib.

OFIE(2)

M41T83 only

Watch-

dog(3)

BMB0-BMB4, RB0, RB1

A1IE (2) SQWE(2) ABE

Initial

power-up

Subsequent

power-up(4)(5)

With battery backup

UC = unchanged

Table 18.

Initial power-up default values (part 2)

Condition(1)

All other control bits power-up in an undetermined state.

RPT11

-15

TI/TP

(2)

M41T83 only

TIE(2) TD1 TD0 RS0 RS1-3

OTP

(2)

A2IE(2)

RPT21-

AL2E

Initial

power-up

Subsequent

power-up(3)(4)

With battery backup

UC = unchanged

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