DS1670S datasheet(4/17 Pages) DALLAS

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DS1670

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POWER-UP/POWER-DOWN CONSIDERATIONS

The DS1670 was designed to operate with a power supply of 3.3 volts. When 3.3 volts are applied within

nominal limits, the device becomes fully accessible after tRPU (250 ms typical). Before tRPU elapses, all

inputs are disabled. When VCC drops below 2.88 volts (typical), the RST pin is driven low. When VCC

drops below the lower of 2.7 volts (typical) or the battery voltage, the device is switched over to the

backup power supply.

During power up, when VCC returns to an in-tolerance condition, the RST pin is kept in the active state

for 250 ms (typical) to allow the power supply and microprocessor to stabilize.

ADDRESS/COMMAND BYTE

The command byte for the DS1670 is shown in Figure 2. Each data transfer is initiated by a command

byte. Bits 0 through 6 specify the addresses of the registers to be accessed. The MSB (bit 7) is the

Read/Write bit. This bit specifies whether the accessed byte will be read or written. A read operation is

selected if bit 7 is a 0 and a write operation is selected if bit 7 is a 1. The address map for the DS1670 is

shown in Figure 3.

ADDRESS/COMMAND BYTE Figure 2

DS1670 ADDRESS MAP Figure 3

BIT 7

BIT 0

10 SECONDS

SECONDS

10 MINUTES

MINUTES

10 HR

A/P

10 HR

HOURS

DAY

10 DATE

DATE

MO.

MONTH

10 YEAR

YEAR

10 SEC ALARM

SECONDS ALARM

10 MIN ALARM

MINUTES ALARM

10 HR

A/P

10 HR

HOUR ALARM

DAY ALARM

CONTROL REGISTER

STATUS REGISTER

WATCHDOG REGISTER

ADC REGISTER

RESERVED

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