9

FN8183.1

September 9, 2005

Pin Descriptions

equivalent to the fixed terminals of a mechanical

relative position of the terminal in relation to wiper movement

direction selected by the U/D input and not the voltage

potential on the terminal.

R

W

terminal of a mechanical potentiometer. The position of the

wiper within the array is determined by the control inputs.

The wiper terminal series resistance is typically 200

Ω.

Up/Down (U/D)

The U/D input controls the direction of the wiper movement

and whether the counter is incremented or decremented.

Increment (INC)

The INC input is negative-edge triggered. Toggling INC will

move the wiper and either increment or decrement the

counter in the direction indicated by the logic level on the

U/D input.

Chip Select (CS)

The device is selected when the CS input is LOW. The

current counter value is stored in nonvolatile memory when

CS is returned HIGH while the INC input is also HIGH. After

the store operation is complete the X9317 will be placed in

the low power standby mode until the device is selected

once again.

Pin Configuration

Principles of Operation

There are three sections of the X9317: the control section,

the nonvolatile memory, and the resistor array. The control

section operates just like an up/down counter. The output of

this counter is decoded to turn on a single electronic switch

connecting a point on the resistor array to the wiper output.

The contents of the counter can be stored in nonvolatile

memory and retained for future use. The resistor array is

comprised of 99 individual resistors connected in series.

Electronic switches at either end of the array and between

each resistor provide an electrical connection to the wiper

The wiper acts like its mechanical equivalent and does not

move beyond the first or last position. That is, the counter

does not wrap around when clocked to either extreme.

The electronic switches on the device operate in a “make

before break” mode when the wiper changes tap positions. If

the wiper is moved several positions, multiple taps are

a significant amount if the wiper is moved several positions.

When the device is powered-down, the last wiper position

stored will be maintained in the nonvolatile memory. When

power is restored, the contents of the memory are recalled

and the wiper is set to the value last stored.

Instructions and Programming

The INC, U/D and CS inputs control the movement of the

wiper along the resistor array. With CS set LOW the device

is selected and enabled to respond to the U/D and INC

inputs. HIGH to LOW transitions on INC will increment or

decrement (depending on the state of the U/D input) a seven

bit counter. The output of this counter is decoded to select

one of one hundred wiper positions along the resistive array.

The value of the counter is stored in nonvolatile memory

whenever CS transitions HIGH while the INC input is also

HIGH.

INC

U/D

1

2

3

4

8

7

6

5

X9317

DIP/SOIC/MSOP

CS

INC

CS

1

2

3

4

8

7

6

5

X9317

TSSOP

U/D

Pin Names

SYMBOL

DESCRIPTION

RH

High terminal

RW

Wiper terminal

RL

Low terminal

VSS

Ground

VCC

Supply voltage

U/D

Up/Down control input

INC

Increment control input

CS

Chip select control input

X9317