X9428 Datasheet, PDF (4/20 Pages) Xicor Inc. – Single Digitally Controlled Potentiometer

X9428
Acknowledge Polling
The disabling of the inputs, during the internal
nonvolatile write operation, can be used to take
advantage of the typical 5ms EEPROM write cycle
time. Once the stop condition is issued to indicate the
end of the nonvolatile write command the X9428
initiates the internal write cycle. ACK polling can be
initiated immediately. This involves issuing the start
condition followed by the device slave address. If the
X9428 is still busy with the write operation no ACK will
be returned. If the X9428 has completed the write
operation an ACK will be returned, and the master can
then proceed with the next operation.
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
Figure 2. Instruction Byte Format
Register
Select
I3 I2 I1 I0 R1 R0 0 0
Instructions
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. Bits 0 and 1 are defined to be 0.
Four of the seven 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.
Four instructions require a three-byte sequence to
complete. These instructions transfer data between the
host and the X9428; 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.
Proceed
Proceed
Instruction Structure
The next byte sent to the X9428 contains the instruction
and register pointer information. The four most
significant bits are the instruction. The next four bits
point to one of four associated registers. The format is
shown below in Figure 2.
REV 1.1.5 7/8/03
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Characteristics subject to change without notice. 4 of 20