X9279 Datasheet, PDF (10/22 Pages) Xicor Inc. – Single Digitally-Controlled (XDCP) Potentiometer

X9279
Table 4. Wiper counter Register, WCR (8-bit), WCR[7:0]: Used to store the current wiper position (Volatile, V).
WCR7
WCR6
WCR5
WCR4
WCR3
WCR2
WCR1
WCR0
V
V
V
V
V
V
V
V
(MSB)
(LSB)
Table 5. Data Register, DR (8-bit), Bit [7:0]: Used to store wiper positions or data (Nonvolatile, NV).
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NV
NV
NV
NV
NV
NV
NV
NV
MSB
LSB
Instructions
Four of the seven instructions are three bytes in
length. These instructions are:
– Read Wiper Counter Register – read the current
wiper position of the potentiometer,
– Write Wiper Counter Register – change current
wiper position of the potentiometer,
– Read Data Register – read the contents of the
selected Data Register;
– Write Data Register – write a new value to the
selected Data Register.
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_WRL. A transfer
from the WCR (current wiper position), to a Data
Register is a write to nonvolatile memory and takes a
minimum of t_WR to complete. The transfer can occur
between the potentiometer and one of its four
associated registers (Bank 0).
Figure 3. Two-Byte Instruction Sequence
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 –
This transfers the contents of one specified Data
Register to the Wiper Counter Register.
– XFR Wiper Counter Register to Data Register –
This transfers the contents of the Wiper Counter
Register to the specified 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_HIGH) while SDA is HIGH,
the selected wiper will move one resistor segment
towards the R_H terminal. Similarly, for each SCL clock
pulse while SDA is LOW, the selected wiper will move
one resistor segment towards the R_L terminal.
See Instruction format for more details.
SCL
SDA
0 101
S ^{ID3 ID2 ID1 ID0} 0 A2 A1 A0
T
A
R Device ID
Internal
T
Address
00
A I3 I2 _{I1 I0} RB RA P1 _P0 A S
C
CT
K
KO
Instruction _Register
Pot/Bank ^P
Opcode
Address
Address
These commands only valid when P1 = P0 = 0
10
FN8175.2
September 27, 2005