X9258 Xicor, X9258 Datasheet - Page 8

• Manufacturer Part Number: X9258
• Description: Quad Digital Controlled Potentiometers (XDCP)
• Manufacturer: Xicor

X9258
Figure 8. Detailed Potentiometer Block Diagram Detailed Operation
REV 1.1.7 2/4/03
All DCP potentiometers share the serial interface and
share a common architecture. Each potentiometer has
a Wiper Counter Register and four Data Registers. A
detailed discussion of the register organization and
array operation follows.
Wiper Counter Register
The X9258 contains four Wiper Counter Registers,
one for each DCP potentiometer. The Wiper Counter
Register can be envisioned as a 8-bit parallel and
serial load counter with its outputs decoded to select
one of 256 switches along its resistor array. The
contents of the WCR can be altered in four ways: it
may be written directly by the host via the Write Wiper
Counter Register instruction (serial load); it may be
written indirectly by transferring the contents of one of
four associated Data Registers via the XFR Data
Register instruction (parallel load); it can be modified
one step at a time by the Increment/Decrement
instruction. Finally, it is loaded with the contents of its
data register zero (R0) upon power-up.
Serial Data Path
From Interface
If WCR = FF[H] then V
If WCR = 00[H] then V
Circuitry
W
W
/R
/R
W
W
Register 0
Register 2
= V
= V
L
H
/R
/R
L
H
8
Register 1
Register 3
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Modified SCL
UP/DN
8
The WCR is a volatile register; that is, its contents are
lost when the X9258 is powered-down. Although the
register is automatically loaded with the value in R0
upon power-up, it should be noted this may be
different from the value present at power-down.
Data Registers
Each
Registers. These can be read or written directly by the
host and data can be transferred between any of the
four Data Registers and the WCR. It should be noted
all operations changing data in one of these registers
is a nonvolatile operation and will take a maximum of
10ms.
If the application does not require storage of multiple
settings for the potentiometer, these registers can be
used as regular memory locations that could possibly
store system parameters or user preference data.
BUS
Input
UP/DN
CLK
Serial
BUS
Input
Parallel
potentiometer
INC/DEC
Register
Counter
(WCR)
Wiper
Logic
Characteristics subject to change without notice.
C
D
c
t
r
o
d
e
o
u
n
e
e
has
four
nonvolatile
V
V
V
H
L
W
/R
/R
/R
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Data
L
H
W