X9511

3

DEVICE OPERATION

There are three sections of the X9511: the input control,

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

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 X9511 is designed to interface directly to two push

button switches for effectively moving the wiper up or

down. The PU and PD inputs increment or decrement a

5-bit counter respectively. The output of this counter is

decoded to select one of the thirty-two wiper positions

along the resistive array. The wiper increment input, PU

and the wiper decrement input, PD are both connected

to an internal pull-up so that they normally remain HIGH.

When pulled LOW by an external push button switch or a

logic LOW level input, the wiper will be switched to the

next adjacent tap position.

Internal debounce circuitry prevents inadvertent switch-

ing of the wiper position if PU or PD remain LOW for less

than 40ms, typical. Each of the buttons can be pushed

either once for a single increment/decrement or continu-

ously for a multiple increments/decrements. The number

of increments/decrements of the wiper position depend

on how long the button is being pushed. When making a

continuous push, after the first second, the increment/

decrement speed increases. For the first second the

device will be in the slow scan mode. Then if the button is

held for longer than 1 second the device will go into the

fast scan mode. As soon as the button is released the

X9511 will return to a standby condition.

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.

AUTOSTORE

ASE is enabled (held LOW). When power is restored, the

content of the memory is recalled and the counter reset

to the last value stored.

If AUTOSTORE is to be implemented, ASE is typically

and then taken LOW, the wiper will not respond to the PU

or PD inputs until ASE is brought HIGH and held HIGH.

Manual (Push Button) Store

When ASE is not enabled (held HIGH) a push button

switch may be used to pull ASE LOW and released to

perform a manual store of the wiper position.

The end to end resistance of the array will fluctuate once

Typical circuit with ASE store pin controlled by

push button switch

PU

PD

ASE

VH

VW

VL

8

1

2

7

3

5

6

3067 ILL F05a

Typical circuit with ASE store pin used in

AUTOSTORE mode

PU

PD

ASE

VH

VW

VL

3.3µF

8

1

2

7

4

3

5

6

3067 ILL F05.2