X9252 Datasheet, PDF (11/21 Pages) Xicor Inc. – Quad Digitally-Controlled (XDCP) potentiometer

X9252
UP/DOWN INTERFACE OPERATION
The SCL, U/D, CS, DS0 and DS1 inputs control the
movement of the wiper along the resistor array. With
CS set LOW the device is selected and enabled to
respond to the U/D and SCL inputs. HIGH to LOW
transitions on SCL will increment or decrement
(depending on the state of the U/D input) a wiper
counter register selected by DS0 and DS1. The output
of this counter is decoded to select one of 256 wiper
positions along the resistor array.
The value of the counter is stored in nonvolatile Data
Registers DRi0 whenever CS transitions HIGH while
the SCL and WP inputs are HIGH. “i” indicates the
DCP number selected with pins DS1 and DS0. During
a “Store” operation bits DRSel1 and DRSel0 in the
Status Register must be both “0”, which is their power
up default value. Other combinations are reserved and
must not be used.
The system may select the X9252, move the wiper,
and deselect the device without having to store the lat-
est wiper position in nonvolatile memory. After the
wiper movement is performed as described above and
once the new position is reached, the system must
keep SCL LOW while taking CS HIGH. The new wiper
postion will be maintained until changed by the system
or until a power-down/up cycle recalled the previousely
stored data.
This procedure allows the system to always power-up
to a preset value stored in nonvolatile memory; then
during system operation minor adjustments could be
made. The adjustments might be based on user prefer-
ence, system parameter changes due to temperaure
drift, etc.
The state of U/D may be changed while CS remains
LOW. This allows the host system to enable the device
and then move the wiper up and down until the proper
trim is attained. The 2-wire interface is disabled while
CS remains LOW.
Table 1. DCP Selection for Up/Down Control
DS1
DS0
Selected DCP
0
0
DCP0
0
1
1
0
DCP1
DCP2
1
1
DCP3
MODE SELECTION FOR UP/DOWN CONTROL
CS SCL U/D
Mode
L
H Wiper Up
L
L Wiper Down
H
X Store Wiper Position to non-
volatile memory if WP pin is
high. No store, return to stand-
by, if WP pin is low.
H
X
X Standby
L
X No Store, Return to Standby
L
H Wiper Up (not recommended)
L
L Wiper Down
(not recommended)
REV 1.4.1 7/29/03
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