X9455 Datasheet, PDF (9/18 Pages) Intersil Corporation – Dual Two-wiper Digitally-Controlled (XDCP) Potentiometer

X9455
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 register
Level 0 of the corresponding WCR whenever CS transitions
HIGH while the SCL and WP inputs are HIGH (See Table 1).
During a “Store” operation bits WCRSel1 and WCRSel0 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 X9455, move a wiper, and
deselect the device without having to store the latest 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 position is maintained until changed
by the system or until a power-down/up cycle recalled the
previously 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 preference, system
parameter changes due to temperature 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
SELECTED WIPER
DS1
DS0
CONTROL REGISTER
0
0
Wiper A of DCP0
1
1
Wiper B of DCP0
1
0
Wiper A of DCP1
0
1
Wiper B of DCP1
TABLE 2. 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 nonvolatile
memory if WP pin is high. No store,
return to standby, 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)
*While in Standby, the 2-wire interface is enabled
9
FN8202.0
November 10, 2004