X9428 Xicor, X9428 Datasheet - Page 4

• Manufacturer Part Number: X9428
• Description: Single Digitally Controlled Potentiometer
• Manufacturer: Xicor

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
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
Command Completed
Enter ACK Polling
Nonvolatile Write
Issue Slave
Operation?
Returned?
Instruction
Address
Proceed
START
Further
Issue
Issue
ACK
YES
YES
NO
NO
Issue STOP
Issue STOP
Proceed
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Figure 2. Instruction Byte Format
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
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
from the Wiper Counter Register (current wiper
position), to a Data Register is a write to nonvolatile
memory and takes a minimum of t
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.
I3
of
Instructions
the
I2
seven
I1
Characteristics subject to change without notice.
I0
instructions
Register
R1
Select
R0
WR
0
to complete.
WRL
end
0
. A transfer
with
4 of 20
the