X9279 Xicor, X9279 Datasheet - Page 10

• Manufacturer Part Number: X9279
• Description: Single Digitally-Controlled (XDCP) Potentiometer
• Manufacturer: Xicor

X9279
Table 4. Wiper counter Register, WCR (8-bit), WCR[7:0]: Used to store the current wiper position (Volatile, V).
Table 5. Data Register, DR (8-bit), Bit [7:0]: Used to store wiper positions or data (Nonvolatile, NV).
REV 1.1.7 2/6/03
Figure 3. Two-Byte Instruction Sequence
Instructions
Four of the seven instructions are three bytes in length.
These instructions are:
– Read Wiper Counter Register – read the current
– Write Wiper Counter Register – change current
– Read Data Register – read the contents of the
– Write Data Register – write a new value to the
The basic sequence of the three byte instructions is
illustrated in Figure 4. These three-byte instructions
exchange data between the WCR and one of the Data
Registers. A transfer from a Data Register to a WCR is
essentially a write to a static RAM, with the static RAM
controlling the wiper position. The response of the
wiper to this action will be delayed by t
from the WCR (current wiper position), to a Data
Register is a write to nonvolatile memory and takes a
minimum of t
between the potentiometer and one of its four
associated registers (Bank 0).
wiper position of the potentiometer,
wiper position of the potentiometer,
selected Data Register;
selected Data Register.
WCR7
(MSB)
MSB
Bit 7
NV
V
SCL
SDA
WR
S
T
A
R
T
WCR6
to complete. The transfer can occur
ID3 ID2 ID1 ID0
Bit 6
NV
0
V
Device ID
1
0
1
WCR5
Bit 5
NV
0 A2
V
Internal
Address
WRL
A1
. A transfer
A0
WCR4
Bit 4
NV
www.xicor.com
A
C
K
V
I3
Instruction
Opcode
I2 I1 I0
Two instructions require a two-byte sequence to
complete. These instructions transfer data between the
host and the X9279; either between the host and one
of the data registers or directly between the host and
the Wiper Counter Register. These instructions are:
– XFR Data Register to Wiper Counter Register –
– XFR Wiper Counter Register to Data Register –
The final command is Increment/Decrement (Figure 5
and 6). The Increment/Decrement command is
different from the other commands. Once the
command is issued and the X9279 has responded with
an acknowledge, the master can clock the selected
wiper up and/or down in one segment steps; thereby,
providing a fine tuning capability to the host. For each
SCL clock pulse (t
selected wiper will move one resistor segment towards
the R
while SDA is LOW, the selected wiper will move one
resistor segment towards the R
See Instruction format for more details.
WCR3
Bit 3
This transfers the contents of one specified Data
Register to the Wiper Counter Register.
This transfers the contents of the Wiper Counter
Register to the specified Data Register.
NV
V
Register
Address
H
RB RA P1
terminal. Similarly, for each SCL clock pulse
These commands only valid when P1=P0=0
0
WCR2
Bit 2
Characteristics subject to change without notice.
NV
Pot/Bank
Address
V
0
P0
HIGH
A
C
K
) while SDA is HIGH, the
S
T
O
P
WCR1
Bit 1
L
NV
V
terminal.
WCR0
(LSB)
Bit 0
LSB
NV
V
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