DS1802

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CASCADE OPERATION

A feature of the DS1802 is the ability to control multiple devices from a single processor. Multiple

DS1802s can be linked or daisy-chained as shown in Figure 7. As a bit is entered in to the I/O shift

multiple devices, the total number of bits sent is always 16 times the number of DS1802s in the daisy

chain.

of the first DS1802, thus allowing the controlling processor to circularly clock data through the daisy

chain. The value of the feedback or isolation resistor should be in the range from 2 k

Ω to 10 kΩ .

the isolation resistor. When the CLK input transitions low to high, bit 0 is loaded into the first position of

times the number of DS1802s in the daisy chain), the data has shifted completely around and back to its

the read occurred) is loaded into the wiper-0 and wiper-1.

CASCADING MULTIPLE DEVICES Figure 7

Zero-Crossing Detection

The DS1802 provides a zero-crossing detection capability when using the 3-Wire Serial interface. Zero-

crossing detection provides a means for minimizing any audible noise that may result from sizable

discrete wiper transitions when using the part in audio applications. The zero-crossing detect feature

allows independent wiper changes only when the two terminals of the potentiometer have equal potentials

a zero-crossing, the wiper position of the potentiometer(s) will change regardless of the state of the input

ZCEN

input deactivates both the 50 ms time requirement and zero-crossing detection.

Zero-crossing detection is also available when using the part in pushbutton operation. When a pushbutton

is activated, the part will change wiper position during the first detected zero-crossing or at the end of a

50 ms time window.

When operating in pushbutton operation with a continuous input pulse, the wiper position will change

once during the initial 1-second time period. This change is dictated by a detected zero-crossing or 50 ms