DS2890

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Figure 3. 1-WIRE POTENTIOMETER FEATURE REGISTER

Feature Register Bit Encoding

b7

b6

b5

b4

b3

b2

b1

b0

PR

NWP

NP

WSV

PC

Feature Register Bit Definitions

Feature Description

Bit(s)

Definition

If 0: logarithmic potentiometer element(s)

PC: potentiometer characteristic

b0

If 1: linear potentiometer element(s)

If 0: wiper setting(s) are non-volatile

WSV: wiper setting volatility

b1

If 1: wiper setting(s) are volatile

NP: number of potentiometers

b3..b2

2 bit binary value representing number of potentiometers:

If 00b: 1 potentiometer

If 01b: 2 potentiometers

If 10b: 3 potentiometers

If 11b: 4 potentiometers

NWP: number of wiper positions

b5..b4

2 bit binary value representing number of wiper positions

for each potentiometer:

If 00b: 32 positions

If 01b: 64 positions

If 10b: 128 positions

If 11b: 256 positions

PR: potentiometer resistance

b7..b6

2 bit binary value representing potentiometer resistance:

If 00b: 5 k

Ω

If 01b: 10 k

Ω

If 10b: 50 k

Ω

If 11b: 100 k

Ω

DS2890 feature values are highlighted:

value

The DS2890 will respond with a feature register value of F3h when a READ CONTROL

REGISTER command is executed, see section “POTENTIOMETER FUNCTION COMMANDS”.

POTENTIOMETER CONTROL REGISTER

The potentiometer control register is used to turn on/off the DS2890 charge pump (see section

“POTENTIOMETER WIPER RESISTANCE AND CHARGE PUMP CONSIDERATIONS” for a

discussion of the charge pump) and has control capabilities for future 1-Wire potentiometers that could

contain multiple resistor elements. The format of the control register is shown in Figure 4.