M41T65(2004) データシートの表示（PDF） - STMicroelectronics

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M41T65
(Rev.:2004)

Serial Access Real-Time Clock with Alarms

STMicroelectronics 

M41T62/63/64/65

Square Wave Output (M41T62/63/64)

The M41T62/63/64 offers the user a programma-

ble square wave function which is output on the

SQW pin. RS3-RS0 bits located in 04h establish

the square wave output frequency. These fre-

quencies 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.

Table 8. Square Wave Output Frequency

Square Wave Bits

RS3

RS2

RS1

0

0

0

0

0

0

0

0

1

0

0

1

0

1

0

0

1

0

0

1

1

0

1

1

1

0

0

1

0

0

1

0

1

1

0

1

1

1

0

1

1

0

1

1

1

1

1

1

The SQW output is an N-channel, open drain out-

put driver for the M41T64, and a full CMOS output

driver for the M41T62/63. The initial power-up de-

fault for the SQW output is 32KHz (except for

M41T64, which defaults disabled).

Square Wave

RS0

Frequency

Units

0

None

–

1

32.768

KHz

0

8.192

KHz

1

4.096

KHz

0

2.048

KHz

1

1.024

KHz

0

512

Hz

1

256

Hz

0

128

Hz

1

64

Hz

0

32

Hz

1

16

Hz

0

8

Hz

1

4

Hz

0

2

Hz

1

1

Hz

Full-time 32KHz Square Wave Output (M41T64)

The M41T64 offers the user a special 32KHz

square wave function which is enabled on power-

up to output on the F32k pin as long as VCC ≥ 1.3V,

and the oscillator is running (ST Bit = '0'). This

function is available within one second (typ) of ini-

tial 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.

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