X9258_14 Datasheet, PDF (5/19 Pages) Intersil Corporation – Quad Digital Controlled Potentiometers

X9258
ACK Polling Sequence
NONVOLATILE WRITE
COMMAND COMPLETED
ENTER ACK POLLING
ISSUE
START
ISSUE SLAVE
ADDRESS
ACK
NO
RETURNED?
YES
FURTHER
NO
OPERATION?
YES
ISSUE
INSTRUCTION
ISSUE STOP
ISSUE STOP
PROCEED
PROCEED
Instruction Structure
The next byte sent to the X9258 contains the instruction and
register pointer information. The four most significant bits are
the instruction. The next four bits point to one of the two
potentiometers and when applicable they point to one of four
associated registers. The format is shown in Figure 2.
.
REGISTER
SELECT
I3 I2 I1 I0 R1 R0 P1 P0
INSTRUCTIONS
WIPER COUNTER
REGISTER SELECT
FIGURE 2. INSTRUCTION BYTE FORMAT
The four high order bits define the instruction. The next 2 bits
(R1 and R0) select one of the four registers that is to be
acted upon when a register oriented instruction is issued.
The last bits (P1, P0) select which one of the four
potentiometers is to be affected by the instruction.
Four of the nine instructions end with the transmission of the
instruction byte. The basic sequence is illustrated in
Figure 3. These two-byte instructions exchange data
between the Wiper Counter Register and one of the data
registers. A transfer from a Data Register to a Wiper Counter
Register is essentially a write to a static RAM. The response
of the wiper to this action will be delayed t_WRL. A transfer
from the Wiper Counter Register (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 one of the four potentiometers and one of its
associated registers; or it may occur globally, wherein the
transfer occurs between all of the potentiometers and one of
their associated registers.
Four instructions require a three-byte sequence to complete.
These instructions transfer data between the host and the
X9258; either between the host and one of the data registers
or directly between the host and the Wiper Counter Register.
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 nonvolatile register) and Write Data
Register (write a new value to the selected data register).
The sequence of operations is shown in Figure 4.
SCL
SDA
S0 1 0
T
A
R
T
1 A3 A2 A1 A0 A I3 I2
C
K
I1 I0 R1 R0 P1 P0 A S
CT
KO
P
FIGURE 3. TWO-BYTE INSTRUCTION SEQUENCE
5
FN8168.6
December 15, 2011