X9316

3

DEVICE OPERATION

There are three sections of the X9316: the input control,

counter and decode section; the nonvolatile memory;

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 resistor array to the wiper output. Under

the proper conditions the contents of the counter can be

stored in nonvolatile memory and retained for future use.

The resistor array is comprised of 31 individual resistors

connected in series. At either end of the array and

between each resistor is an electronic switch that trans-

fers the potential at that point to the wiper.

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

wiper along the resistor array. With CS set LOW the

X9316 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 thirty two wiper positions

along the resistive array.

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 value of the counter is stored in nonvolatile memory

whenever CS transistions HIGH while the INC input is

also HIGH.

When the X9316 is powered-down, the last counter posi-

tion stored will be maintained in the nonvolatile memory.

When power is restored, the contents of the memory are

recalled and the counter is reset to the value last stored.

Operation Notes

The system may select the X9316, move the wiper and

deselect the device without having to store the latest

wiper position in nonvolatile memory. The wiper move-

ment is performed as described above; once the new

position is reached, the system would the keep INC LOW

while taking CS HIGH. The new wiper position would be

maintained until changed by the system or until a power-

up/down cycle recalled the previously stored data.

This would allow the system to always power-up to a pre-

set value stored in nonvolatile memory; then during sys-

tem 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 X9316

and then move the wiper up and down until the proper

trim is attained.

The electronic switches on the X9316 operate in a “make

before break” mode when the wiper changes tap posi-

tions. If the wiper is moved several positions multiple taps

reduced by a significant amount if the wiper is moved

several positions.

SYMBOL TABLE

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