Datasheet

Clock operation M41T80

16/27 Doc ID 9074 Rev 5

3.3 Full-time 32 KHz square wave output

The M41T80 offers the user a special 32 KHz square wave function which defaults to output

on the F

32K

pin (pin 3) as long as V

is valid, and the oscillator is running (ST bit = '0'). This

function is available within four seconds of initial power-up and can only be disabled by

setting the 32KE bit to '0' or the ST bit to '1.' If not used, the F

32K

pin should be disconnected

and allowed to float.

Note: The F

32K

pin is an open drain which requires an external pull-up resistor.

3.4 Century bit

Bits D7 and D6 of clock register 03h contain the CENTURY ENABLE bit (CEB) and the

CENTURY bit (CB). Setting CEB to a '1' will cause CB to toggle, either from a '0' to '1' or

from '1' to '0' at the turn of the century (depending upon its initial state). If CEB is set to a '0,'

CB will not toggle.

Table 5. Square wave output frequency

Square wave bits Square wave

RS3 RS2 RS1 RS0 Frequency Units

0000None-

000132.768kHz

00108.192kHz

00114.096kHz

01002.048kHz

01011.024kHz

0110512Hz

0111256Hz

1000128Hz

100164Hz

101032Hz

101116Hz

11008Hz

11014Hz

11102Hz

11111Hz