7

FN8185.1

September 14, 2005

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) the 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 X9319, 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 powerup/down cycle recalled the previ-

ously stored data. This procedure allows the system to

always power-up to a preset value stored in nonvola-

tile memory; then during system operation minor

adjustments could be made. The adjustments might

be based on user preference, system parameter

changes due to temperature 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

CS

INC

U/D

Mode

L

H

Wiper up

L

L

Wiper down

HX

Store wiper position to

nonvolatile memory

H

X

X

Standby

L

X

No store, return to standby

L

H

Wiper Up (not recommended)

LL

Wiper Down

(not recommended)

X9319