DS1677(2000) View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated

Part Name

Description

Manufacturer

DS1677
(Rev.:2000)

Portable System Controller

Dallas Semiconductor -> Maxim Integrated 

DS1677

X1, X2 – Connections for a standard 32.768 kHz quartz crystal. For greatest accuracy, the DS1677 must

be used with a crystal that has a specified load capacitance of 6 pF. There is no need for external

capacitors or resistors. Note: X1 and X2 are very high impedance nodes. It is recommended that they

and the crystal be guard–ringed with ground and that high frequency signals be kept away from the

crystal area. For more information on crystal selection and crystal layout considerations, please consult

Application Note 58, “Crystal Considerations with Dallas Real Time Clocks”.

The DS1677 will not function without a crystal.

POWER–UP/POWER–DOWN CONSIDERATIONS

When VCC is applied to the DS1677 and reaches a level greater than VCCTP (power–fail trip point), the

device becomes fully accessible after tRPU (250 ms typical). Before tRPU elapses, all inputs are disabled.

When VCC drops below VCCSW, the device is switched over to the VBAT 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 DS1677 is shown in Figure 2. Each data transfer is initiated by a command

byte. Bits 0 through 6 specify the address 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 zero and a write operation is selected if bit 7 is a one. The address map for the

DS1677 is shown in Figure 3.

ADDRESS/COMMAND BYTE Figure 2

7

6

5

4

3

2

1

0

RD

WR

A6

A5

A4

A3

A2

A1

A0

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