M41T50

14/23

Square Wave Output

The M41T50 offers the user a 1Hz square wave

function which is output on the SQW pin. The

SQW pin can be turned on and off under software

control with the Square Wave Enable Bit (SQWE)

located in Register 0Ah.

The SQW output is programmable as an N-chan-

nel, open drain output driver, or a full CMOS out-

put driver. The initial power-up default for the SQW

output is disabled, in the full-CMOS (or Push-pull

mode). By setting the Square Wave Open Drain

Bit (SQWOD in address 0Ch) to a '1,' the output

specified in Table 9., page 17). When SQWOD is

set to '0,' the output will be configured as full-

CMOS (sink and source current as specified in Ta-

ble 9., page 17).

Note:

When

configured

as

Open

Drain

(SQWOD = '1'), the SQW pin requires an external

pull-up resistor.

Century Bits

These two bits will increment in a binary fashion at

the turn of the century, and handle all leap years

correctly. See Table 5., page 14 for additional ex-

planation.

Output Driver Pin

When the AFE Bit is not set to generate an inter-

rupt, the IRQ/OUT pin becomes an output driver

that reflects the contents of D7 of the Out Register.

In other words, when D7 (OUT Bit) is a '0,' then the

IRQ/OUT pin will be driven low.

Note: The IRQ/OUT pin is an open drain which re-

quires an external pull-up resistor.

Initial Power-on Defaults

Upon application of power to the device, the regis-

ter bits will initially power-on in the state indicated

in Table 4.

Table 4. Initial Power-on Default Values

Note: 1. All other control bits power-up in an undetermined state.

Table 5. Century Bits Examples

Note: 1. Leap year occurs every four years (for years evenly divisible by four), except for years evenly divisible by 100. The only exceptions

are those years evenly divisible by 400 (the year 2000 was a leap year, year 2100 is not).

Condition

ST

SQWOD

OUT

AFE

SQWE

60Hz

Initial

001

00

1

CB0

CB1

Leap Year?

00

Yes

2000

0

1

No

2100

1

0

No

2200

1

1

No

2300