X9259 Datasheet, PDF (9/21 Pages) Xicor Inc. – Quad Digitally-Controlled (XDCP) Potentiometers

X9259
Instructions
Four of the nine instructions are three bytes in length. These
instructions are:
• Read Wiper Counter Register – read the current wiper
position of the selected potentiometer,
• Write Wiper Counter Register – change current wiper
position of the selected 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 5. 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 is delayed by t_WRL. A transfer from the WCR
(current wiper position), to a Data Register is a write to non-
volatile memory and takes a minimum of t_WR to complete.
The transfer can occur between one of the four
potentiometer’s WCR, and one of its associated registers,
DRs; or it may occur globally, where the transfer occurs
between all potentiometers and one associated register.
Four instructions require a two-byte sequence to complete.
These instructions transfer data between the host and the
X9259; 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 associated Wiper Counter Register.
• XFR Wiper Counter Register to Data Register – This
transfers the contents of the specified Wiper Counter
Register to the specified associated Data Register.
• Global XFR Data Register to Wiper Counter
Register – This transfers the contents of all specified Data
Registers to the associated Wiper Counter Registers.
• Global XFR Wiper Counter Register to Data
Register – This transfers the contents of all Wiper
Counter Registers to the specified associated Data
Registers.
Increment/Decrement Command
The final command is Increment/Decrement (Figure 6 and
7). The Increment/Decrement command is different from the
other commands. Once the command is issued and the
X9259 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 moves one wiper position towards the R_H
terminal. Similarly, for each SCL clock pulse while SDA is
LOW, the selected wiper moves one resistor wiper position
towards the R_L terminal.
See Instruction format for more details.
SCL
SDA
0101
S ^{ID3 ID2 ID1 ID0} A3 A2 A1 A0 A I3 I2 I1 I0 RB RA P1 P0 A ^S
T
C
CT
A
R
T
Device ID
External
Address
K
Instruction
Opcode
KO
Register DCP/WCR ^P
Address Address
FIGURE 4. TWO-BYTE INSTRUCTION SEQUENCE
SCL
SDA
0 101
S
T
ID3 ID2 ID1 ID0 A3
A
R Device ID
T
A2 A1 A0
External
Address
A I3
C
K
I2 I1 I0
Instruction
Opcode
RB RA P1 P0 A
C
K
Register Pot/WCR
Address Address
D7 D6 D5 D4 D3 D2 D1 D0 A S
CT
KO
Data for WCR[7:0] or DR[7:0]
P
FIGURE 5. THREE-BYTE INSTRUCTION SEQUENCE 2-WIRE INTERFACE
9
FN8169.2
September 16, 2005