X9258
Figure 3. Two-Byte Instruction Sequence
SCL
SDA
S
T
A
R
T
0
1
0
1
A3 A2 A1 A0
A
C
K
I3 I2
I1 I0 R1 R0 P1 P0
A
C
K
S
T
O
P
The Increment/Decrement command is different from
the other commands. Once the command is issued
and the X9258 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
Similarly, for each SCL clock pulse while SDA is LOW,
the selected wiper will move one resistor segment
towards the V /R terminal. A detailed illustration of
L
L
the sequence and timing for this operation are shown
in Figures 5 and 6 respectively.
(t
) while SDA is HIGH, the selected wiper will
HIGH
move one resistor segment towards the V terminal.
H
Table 1. Instruction Set
Instruction Set
Instruction
I
I
I
I
R
R
P
P
Operation
1/0 1/0 Read the contents of the Wiper Counter Register
pointed to by P - P
3
2
1
0
1
0
1
0
Read Wiper Counter
Register
1
1
1
1
1
0
0
1
0
1
0
1
0
0
1
0
Write Wiper Counter
Register
0
0
1
1
1
1
0
0
0
0
1/0 1/0 Write new value to the Wiper Counter Register
pointed to by P - P
1
0
Read Data Register
1/0 1/0 1/0 1/0 Read the contents of the Data Register pointed
to by P - P and R - R
1
0
1
0
Write Data Register
1/0 1/0 1/0 1/0 Write new value to the Data Register pointed to
by P - P and R - R
1
0
1
0
XFR Data Register to
Wiper Counter Register
1/0 1/0 1/0 1/0 Transfer the contents of the Data Register pointed
to by P - P and R - R to its associated Wiper
1
0
1
0
Counter Register
XFR Wiper Counter
Register to Data
Register
1
0
1
0
1
0
0
0
1
0
0
1
0
1
0
0
1/0 1/0 1/0 1/0 Transfer the contents of the Wiper Counter Reg-
ister pointed to by P - P to the Data Register
1
0
0
pointed to by R - R
1
Global XFR Data
Registers to Wiper
Counter Registers
1/0 1/0
1/0 1/0
0
0
0
0
Transfer the contents of the Data Registers
pointed to by R - R of all four pots to their re-
spective Wiper Counter Registers
1
0
Global XFR Wiper
Counter Registers
to Data Register
Transfer the contents of both Wiper Counter
Registers to their respective data Registers
pointed to by R - R of all four pots
1
0
Increment/Decrement
Wiper Counter Register
0
0
1/0 1/0 Enable Increment/decrement of the ControlLatch
pointed to by P - P
1
0
Note: (1) 1/0 = data is one or zero
FN8168.1
5
May 6, 2005
INTERSIL [ Intersil ]
