X9110 datasheet(4/21 Pages) XICOR

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X9110 – Preliminary Information

Characteristics subject to change without notice.

4 of 21

REV 1.1.4 11/13/00

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PIN DESCRIPTIONS

Bus Interface Pins

SERIAL OUTPUT (SO)

SO is a serial data output pin. During a read cycle,

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

the falling edge of the serial clock.

SERIAL INPUT (SI)

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

addresses and data to be written to the pots and pot

registers 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

X9110.

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.

DEVICE ADDRESS (A0)

The address input is used to set the 8-bit slave

address. A match in the slave address serial data

stream A0 must be made with the address input (A0) in

order to initiate communication with the X9110.

CHIP SELECT (CS)

When CS is HIGH, the X9110 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 X9110, 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.

HARDWARE WRITE PROTECT INPUT (WP)

The WP pin when LOW prevents nonvolatile writes to

the Data Registers.

Potentiometer Pins

RH, RL

The RH and RL pins are equivalent to the terminal

connections on a mechanical potentiometer.

The wiper pin are equivalent to the wiper terminal of a

mechanical potentiometer.

Bias Supply Pins

SYSTEM SUPPLY VOLTAGE (VCC) AND SUPPLY GROUND (VSS)

The VCC pin is the system supply voltage. The VSS pin

is the system ground.

ANALOG SUPPLY VOLTAGES (V+ AND V

These supplies are the analog voltage supplies for the

potentiometer. The V+ supply is tied to the wiper

switches while the V- supply is used to bias the

switches and the internal P+ substrate of the integrated

circuit. Both of these supplies set the voltage limits of

the potentiometer.

PRINCIPLES OF OPERATION

DEVICE DESCRIPTION

Serial Interface

The X9110 supports the SPI interface hardware

conventions. The device is accessed via the SI input

with data clocked-in on the rising SCK. CS must be

LOW and the HOLD and WP pins must be HIGH

during the entire operation.

The SO and SI pins can be connected together, since

they have three state outputs. This can help to reduce

system pin count.

Array Description

The X9110 is comprised of a resistor array (Figure 1).

The array contains the equivalent of 1023 discrete

resistive segments that are connected in series. The

physical ends of each array are equivalent to the ﬁxed

terminals of a mechanical potentiometer (RH and RL

inputs).

At both ends of each array and between each resistor

segment is a CMOS switch connected to the wiper

(RW) output. Within the individual array only one switch

may be turned on at a time.

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