X9420

FN8195 Rev.1.00

Page 3 of 19

April 26, 2006

PIN DESCRIPTIONS

Host Interface Pins

Serial Output (SO)

SO is a push/pull serial data output pin. During a read

cycle, data is shifted out on this pin. Data is clocked out

by the falling edge of the serial clock.

Serial Input

SI is the serial data input pin. All opcodes, byte

addresses and data to be written to the potentiometer

and pot register are input on this pin. Data is latched by

the rising edge of the serial clock.

Serial Clock (SCK)

The SCK input is used to clock data into and out of the

X9420.

Chip Select (CS)

When CS is HIGH, the X9420 is deselected and the SO

pin is at high impedance, and (unless an internal write

cycle is underway) the device will be in the standby

state. CS LOW enables the X9420, placing it in the

active power mode. It should be noted that after a

power-up, a HIGH to LOW transition on CS is required

prior to the start of any operation.

Hold (HOLD)

HOLD is used in conjunction with the CS pin to select

the device. Once the part is selected and a serial

sequence is underway, HOLD may be used to pause the

serial communication with the controller without resetting

the serial sequence. To pause, HOLD must be brought

LOW while SCK is LOW. To resume communication,

HOLD is brought HIGH, again while SCK is LOW. If the

pause feature is not used, HOLD should be held HIGH

at all times.

The address inputs is used to set the least significant bit

of the 8-bit slave address. A match in the slave address

serial data stream must be made with the address input

in order to initiate communication with the X9420. A

maximum of 2 devices may occupy the SPI serial bus.

Potentiometer Pins

connections on either end of a mechanical potentiometer.

The wiper output is equivalent to the wiper output of a

mechanical potentiometer.

Hardware Write Protect Input (WP)

The WP pin when LOW prevents nonvolatile writes to

the Data Registers. Writing to the Wiper Counter

Register is not restricted.

Analog Supplies (V+, V-)

The analog supplies V+, V- are the supply voltages for

the XDCP analog section.

PIN CONFIGURATION

CS

SI

WP

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

V+

NC

A0

SO

HOLD

SCK

NC

V-

DIP/SOIC

X9420

TSSOP

CS

SI

WP

1

2

3

4

5

6

7

14

13

12

11

10

9

8

V+

A0

SO

HOLD

SCK

V-

X9420