X9015

3

PRINCIPLES OF OPERATION

There are two sections of the X9015: the input control,

counter and decode section; and the resistor array. The

input 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 resis-

tor array to the wiper output. The resistor array is com-

prised of 31 individual resistors connected in series.

The wiper, when at either fixed terminal, acts like its

mechanical equivalent and does not move beyond the

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

temporarily be reduced by a significant amount if the

wiper is moved several positions.

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

lost. When power is restored, the wiper is set to tap #15.

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 five bit counter. The output of this counter is

decoded to select one of thirty two wiper positions along

the resistive array.

The system may select the X9015, move the wiper and

deselect the device. The new wiper position will be

maintained until changed by the system or until a power-

up/down cycle.

The state of U/D may be changed while CS remains

LOW. This allows the host system to enable the device

and then move the wiper up and down until the proper

trim is attained.

MODE SELECTION

SYMBOL TABLE

CS

INC

U/D

Mode

L

H

Wiper Up

L

L

Wiper Down

H

X

X

Standby Current

L

X

Return to standby

WAVEFORM

INPUTS

OUTPUTS

Must be

steady

Will be

steady

May change

from Low to

High

Will change

from Low to

High

May change

from High to

Low

Will change

from High to

Low

Don’t Care:

Changes

Allowed

Changing:

State Not

Known

N/A

Center Line

is High

Impedance