X9241A_07 Datasheet, PDF (5/16 Pages) Intersil Corporation – Quad Digital Controlled Potentionmeters (XDCP™)

X9241A
Flow 1. ACK Polling Sequence
NONVOLATILE WRITE
COMMAND COMPLETED
ENTER ACK POLLING
ISSUE
START
ISSUE SLAVE
ADDRESS
ISSUE STOP
ACK
NO
RETURNED?
YES
FURTHER
NO
OPERATION?
YES
ISSUE
INSTRUCTION
ISSUE STOP
PROCEED
PROCEED
Instruction Structure
The next byte sent to the X9241A contains the instruction
and register pointer information. The 4 most significant bits
are the instruction. The next 4-bits point to one of four pots
and when applicable they point to one of four associated
registers. The format is in Figure 2.
POTENTIOMETER
SELECT
I3 I2 I1 I0 P1 P0 R1 R0
INSTRUCTIONS
REGISTER
SELECT
FIGURE 2. INSTRUCTION BYTE FORMAT
The 4 high order bits define the instruction. The next 2-bits
(P1 and P0) select which one of the four potentiometers is to
be affected by the instruction. The last 2-bits (R1 and R0)
select one of the four registers that are to be acted upon
when a register oriented instruction is issued.
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 WCR
and one of the data registers. A transfer from a Data Register
to a WCR is essentially a write to a static RAM. The response
of the wiper to this action will be delayed t_STPWV. A transfer
from WCR 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 four 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
X9241A; either between the host and one of the Data
Registers or directly between the host and the WCR. These
instructions are: Read WCR, read the current wiper position
of the selected pot; Write WCR, change current wiper
position of the selected pot; Read Data Register, read the
contents of the selected nonvolatile register; 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
X9241A 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 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 is shown in
Figures 5 and 6 respectively.
SCL
SDA
S 0 1 0 1 A3 A2 A1 A0 _A I3 I2 I1 I0 P1 P0 R1 R0 A S
T
C
CT
A
K
KO
R
P
T
FIGURE 3. TWO-BYTE INSTRUCTION SEQUENCE
5
FN8164.6
August 31, 2007