X9408_14 Datasheet, PDF (5/20 Pages) Intersil Corporation – Quad Digitally Controlled Potentiometers

Flow 1. ACK Polling Sequence
NON-VOLATILE WRITE
COMMAND COMPLETED
ENTER ACK POLLING
ISSUE
START
X9408
REGISTER
SELECT
I3 I2 I1 I0 R1 R0 P1 P0
INSTRUCTIONS
WIPER COUNTER
REGISTER SELECT
FIGURE 2. INSTRUCTION BYTE FORMAT
ISSUE SLAVE
ADDRESS
ACK
NO
RETURNED?
YES
FURTHER
NO
OPERATION?
YES
ISSUE
INSTRUCTION
PROCEED
ISSUE STOP
ISSUE STOP
PROCEED
Instruction Structure
The next byte sent to the X9408 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 pots
and when applicable they point to one of four associated
registers. The format is shown in Figure 2.
The four high order bits define the instruction. The next two
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
X9408; 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 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.
SCL
SDA
S 0 1 0 1 A3 A2 A1 A0 A I3 I2 I1 I0 R1 R0 P1 P0 A S
T
C
CT
A
K
KO
R
P
T
FIGURE 3. TWO-BYTE INSTRUCTION SEQUENCE
5
FN8191.4
January 15, 2009