3
FN8195.1
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.
Device Address (A
0
)
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
V
H
/R
H
, V
L
/R
L
The V
H
/R
H
and V
L
/R
L
input are equivalent to the
terminal connections on either end of a mechanical
potentiometer.
V
W
/R
W
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.
System/Digital Supply (V
CC
)
V
CC
is the supply voltage for the system/digital
section. V
SS
is the system ground.
PIN CONFIGURATION
V
CC
CS
R
L
/V
L
SI
WP
V
SS
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
R
H
/V
H
R
W
/V
W
TSSOP
V
CC
CS
R
L
/V
L
SI
WP
V
SS
1
2
3
4
5
6
7
14
13
12
11
10
9
8
V+
A0
SO
HOLD
SCK
V-
X9420
R
H
/V
H
R
W
/V
W
X9420
