X9429
Figure 3. Two-Byte Instruction Sequence
SCL
SDA
S
T
A
R
T
0
1
0
1
A3
A2
0
A0
A
C
K
I3
I2
I1
I0
R1 R0 0
0
A
C
K
S
T
O
P
Read Wiper Counter Register (read the current wiper
position of the selected pot), write Wiper Counter
Register (change current wiper position of the selected
pot), read Data Register (read the contents of the
selected nonvolatile register) and write Data Register
(write a new value to the selected Data Register). The
sequence of operations is shown in Figure 4.
The Increment/Decrement command is different from
the other commands. Once the command is issued
and the X9429 has responded with an acknowledge,
Table 1. Instruction Set
Instruction
Read Wiper Counter
Register
Write Wiper Counter
Register
Read Data Register
Write Data Register
XFR Data Register to
Wiper Counter Register
XFR Wiper Counter
Register to Data Regis-
ter
Increment/Decrement
Wiper Counter Register
Note:
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 V
H
/R
H
terminal. Similarly, for each SCL clock pulse while
SDA is LOW, the selected wiper will move one resistor
segment towards the V
L
/R
L
terminal. A detailed
illustration of the sequence and timing for this
operation are shown in Figures 5 and 6 respectively.
I
3
1
1
1
1
1
1
0
I
2
0
0
0
1
1
1
0
Instruction Set
I
1
I
0
R
1
R
0
0
1
1
0
0
1
1
1
0
1
0
1
0
0
0
0
0
0
X
1
0
0
0
0
0
0
0
X
0
0
0
0
0
0
0
0
Operation
Read the contents of the Wiper Counter Register
Write new value to the Wiper Counter Register
Read the contents of the Data Register pointed to
by R
1
- R
0
Write new value to the Data Register pointed to by
R
1
- R
0
Transfer the contents of the Data Register pointed
to by R
1
- R
0
to its Wiper Counter Register
Transfer the contents of the Wiper Counter Register
to the Data Register pointed to by R
1
- R
0
Enable Increment/decrement of the Wiper Counter
Register
1/0 1/0
1/0 1/0
1/0 1/0
1/0 1/0
0
0
(1) 1/0 = data is one or zero
7
FN8248.2
October 19, 2005
INTERSIL [ INTERSIL CORPORATION ]
