8

FN8222.1

December 20, 2006

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 mem-

ory whenever CS transitions HIGH while the INC input

is also HIGH.

The system may select the X9Cxxx, move the wiper,

and deselect the device without having to store the lat-

est wiper position in nonvolatile memory. After the

wiper movement is performed as described above and

once the new position is reached, the system must

keep INC LOW while taking CS HIGH. The new wiper

position will be maintained until changed by the sys-

tem or until a power-down/up cycle recalled the previ-

ously stored data.

This procedure allows the system to always power-up

to a preset value stored in nonvolatile memory; then

during system operation minor adjustments could be

made. The adjustments might be based on user pref-

erence: system parameter changes due to tempera-

ture drift, etc...

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

Store Wiper Position

H

X

X

Standby Current

L

X

No Store, Return to Standby

L

H

Wiper Up (not recommended)

L

L

Wiper Down (not recommended)

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

X9C102, X9C103, X9C104, X9C503