X9250
The four high order bits of the instruction byte specify
Five instructions require a three-byte sequence to
complete. These instructions transfer data between the
host and the X9250; either between the host and one of
the data registers or directly between the host and the
Wiper Counter Register.These instructions are:
the operation. The next two bits (R and R ) select one
1
0
of the four registers that is to be acted upon when a
register oriented instruction is issued. The last two bits
(P1 and P ) selects which one of the four
0
potentiometers is to be affected by the instruction.
– Read Wiper Counter Register—read the current
wiper position of the selected pot,
Four of the ten instructions are two bytes in length and
end with the transmission of the instruction byte. These
instructions are:
– Write Wiper Counter Register—change current wiper
position of the selected pot,
– XFR Data Register to Wiper Counter Register—This
transfers the contents of one specified Data Register
to the associated Wiper Counter Register.
– Read Data Register—read the contents of the
selected data register;
– Write Data Register—write a new value to the
selected data register.
– XFR Wiper Counter Register to Data Register—This
transfers the contents of the specified Wiper Counter
Register to the specified associated Data Register.
– Read Status—This command returns the contents of
the WIP bit which indicates if the internal write cycle
is in progress.
– Global XFR Data Register to Wiper Counter Register—
This transfers the contents of all specified Data Reg-
isters to the associated Wiper Counter Registers.
The sequence of these operations is shown in Figure 5
and Figure 6.
– Global XFR Wiper Counter Register to Data Register—
This transfers the contents of all Wiper Counter Reg-
isters to the specified associated Data Registers.
The final command is Increment/Decrement. It is
different from the other commands, because it’s length
is indeterminate. Once the command is issued, the
master can clock the selected wiper up and/or down in
one resistor segment steps; thereby, providing a fine
tuning capability to the host. For each SCK clock pulse
The basic sequence of the two byte instructions is
illustrated in Figure 4. 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, with the static RAM
controlling the wiper position.The response of the wiper
(t
) while SI is HIGH, the selected wiper will move
HIGH
one resistor segment towards the V /R terminal.
H
H
Similarly, for each SCK clock pulse while SI is LOW, the
selected wiper will move one resistor segment towards
to this action will be delayed by t
. A transfer from
WRL
the WCR (current wiper position), to a Data Register is
a write to nonvolatile memory and takes a minimum of
the V /R terminal. A detailed illustration of the sequence
L
L
and timing for this operation are shown in Figure 7 and
Figure 8.
t
to complete.The transfer can occur between one of
WR
the four potentiometers and one of its associated
registers; or it may occur globally, where the transfer
occurs between all potentiometers and one associated
register.
Characteristics subject to change without notice. 5 of 21
REV 1.1.5 1/31/03
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