DS2890

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Figure 4. POTENTIOMETER CONTROL REGISTER

Control Register Bit Encoding

b7

b6

b5

b4

b3

b2

b1

b0

XCPC

X

X

WN

WN

Control Register Bit Definitions*

Description

Bit(s)

Definition

WN: wiper number to control

b1..b0

2 bit binary value representing the potentiometer wiper to

control:

If 00b: potentiometer 1 wiper

If 01b: potentiometer 2 wiper

If 10b: potentiometer 3 wiper

If 11b: potentiometer 4 wiper

WN : inverted wiper number to

control

b3..b2

1’s complement of potentiometer wiper to control:

If 11b: potentiometer 1 wiper

If 10b: potentiometer 2 wiper

If 01b: potentiometer 3 wiper

If 00b: potentiometer 4 wiper

If 0: the charge pump is OFF

CPC: charge pump control

b6

If 1: the charge pump is ON

X: don’t care.

b4,b5,b7

These bits are reserved for future use by Dallas

Semiconductor. These bits should be written to a value of

0.

*NOTE:

Control Register power-on defaults: Charge Pump is OFF (CPC=0), Wiper Number to control is wiper #1

(WN=00b, WN =11b).

Valid DS2890 control values are highlighted:

value

Thus for the DS2890, valid control register values are:

Control Register Value

Description

00001100b

charge pump off, potentiometer #1 wiper selected

01001100b

charge pump on, potentiometer #1 wiper selected

As shown in Figure 17 and discussed in the “POTENTIOMETER FUNCTION COMMANDS” section,

no change in device state will occur if an invalid control register value is sent.