X9421 datasheet(4/20 Pages) RENESAS

4 / 20 page

X9421

FN8196 Rev.1.00

Page 4 of 20

January 14, 2009

X9421

(14 LD TSSOP)

TOP VIEW

X9421

(16 LD SOIC)

TOP VIEW

Pin Assignments

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 X9421.

CHIP SELECT (CS)

When CS is HIGH, the X9421 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 X9421, 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.

DEVICE ADDRESS (A0)

The address input 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

RW/VW

VCC

HOLD

SCK

RL/VL

RH/VH

VSS

SCK

VSS

VCC

RL/VL

RH/VH

RW/VW

ISEN

TSSOP

PIN NO.

SOIC

PIN NO.

SYMBOL

DESCRIPTION

Serial Data Output

2, 3

3, 1, 7, 5

No Connect

Chip Select

SCK

Serial Clock

Serial Data Input

VSS

System Ground

Hardware Write Protect

Device Address

HOLD

Device select. Pause the serial bus.

RW/VW

Wiper Terminal of the Potentiometer.

RH/VH

High Terminal of the Potentiometer.

RL/VL

Low Terminal of the Potentiometer.

VCC

System Supply Voltage

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