DS1677

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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

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

765432

10

RD

WR

A6

A5

A4

A3

A2

A1

A0