M41T62 datasheet(28/41 Pages) STMICROELECTRONICS

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Clock operation

M41T62/63/64/65

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Doc ID 10397 Rev 14

3.6

Square wave output (M41T62/63/64)

The M41T62/63/64 offers the user a programmable square wave function which is output on

the SQW pin. RS3-RS0 bits located in 04h establish the square wave output frequency.

These frequencies are listed in Table 8. Once the selection of the SQW frequency has been

completed, 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 an N-channel, open drain output driver for the M41T64, and a full CMOS

output driver for the M41T62/63. The initial power-up default for the SQW output is 32 KHz

(except for M41T64, which defaults disabled).

3.7

Full-time 32 KHz square wave output (M41T64)

The M41T64 offers the user a special 32 KHz square wave function which is enabled on

power-up to output on the F32K pin as long as VCC ≥ 1.3 V, and the oscillator is running

(ST bit = '0'). This function is available within one second (typ) 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 F32K pin

should be disconnected and allowed to float.

Table 8.

Square wave output frequency

Square wave bits

Square wave

RS3

RS2

RS1

RS0

Frequency

Units

0000

None

–

0001

32.768

kHz

0010

8.192

kHz

0011

4.096

kHz

0100

2.048

kHz

0101

1.024

kHz

0110

512

0111

256

1000

128

1001

1010

1011

11008

11014

11102

11111

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