Rainbow-electronics DS1337 Manual de usuario descargar pdf (Pagina 6)

DS1337 I

C Serial Real-Time Clock

6 of 15

BLOCK DIAGRAM

OPERATION

The Block Diagram shows the main elements of the DS1337. As shown, communications to and from the DS1337

occur serially over an I

C bus. The DS1337 operates as a slave device on the serial bus. Access is obtained by

implementing a START condition and providing a device identification code, followed by data. Subsequent

registers can be accessed sequentially until a STOP condition is executed. The device is fully accessible when V

is ³ 1.8V. The DS1337 maintains the time and date when V

is as low as 1.3V.

OSCILLATOR CIRCUIT

The DS1337 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or

capacitors to operate. Table 1 specifies several crystal parameters for the external crystal. Figure 1 shows a

functional schematic of the oscillator circuit. The startup time is usually less than 1 second when using a crystal

with the specified characteristics.

Table 1. Crystal Specifications*

PARAMETER SYMBOL MIN TYP MAX UNITS

Nominal Frequency f

32.768 kHz

Series Resistance ESR 45

Load Capacitance C

6 pF

*The crystal, traces, and crystal input pins should be isolated from RF generating signals. Refer to

Application Note 58: Crystal Considerations for Dallas Real-Time Clocks for additional specifications.

LARM,

TRICKLE

CHARGE, AND

CONTROL

REGISTERS

SERIAL BUS

INTERFACE AND

DDRESS

OSCILLATOR

AND

DIVIDER

CONTROL

LOGIC

SCL

SDA

1Hz

1Hz/4.096kHz/8.192kHz/32.768kHz

MUX/

BUFFER

SQW/INT

USER BUFFER

(7 BYTES)

CLOCK AND

CALENDAR

REGISTERS

"C" VERSION

ONLY

Dallas

Semiconductor

DS1337

1 2 3 4 5 6 7 8 9 10 11 ... 14 15

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Rainbow-electronics DS1337 Manual de usuario Pagina 6

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