X9271_11 Datasheet, PDF (7/22 Pages) Intersil Corporation – Single, Digitally Controlled (XDCP™) Potentiometer

X9271
DEVICE DESCRIPTION
Wiper Counter Register (WCR)
The X9271 contains a Wiper Counter Register (WCR)
for the DCP potentiometer. The WCR can be
envisioned as an 8-bit parallel and serial load counter,
with its outputs decoded to select one of 256 switches
along its resistor array (Table 1). The contents of the
WCR can be altered in four ways:
1. It can be written directly by the host via the Write Wiper
Counter Register instruction (serial load).
2. It can be written indirectly by transferring the contents of
one of four associated data registers via the XFR Data
Register instruction (parallel load).
3. It can be modified one step at a time by the Increment/
Decrement instruction.
4. It is loaded with the contents of its Data Register zero
(DR0) upon power-up.
The WCR is a volatile register; that is, its contents are
lost when the X9271 is powered down. Although the
register is automatically loaded with the value in DR0
upon power-up, this may be different from the value
present at power-down. Power-up guidelines are
recommended to ensure proper loading of the R0
value into the WCR. The DR0 value of Bank 0 is the
default value.
Data Registers (DR3–DR0)
The potentiometer has four 8-bit nonvolatile Data
Registers. These can be read or written directly by the
host (Table 2). Data can also be transferred between
any of the four Data Registers and the associated
WCR. All operations changing data in one of the Data
Registers are nonvolatile operations and take a
maximum of 10ms.
If the application does not require storage of multiple
settings for the potentiometer, the Data Registers can
be used as regular memory locations for system
parameters or user preference data.
Bits [7:0] are used to store one of the 256 wiper
positions or data (0 ~255).
Status Register (SR)
The 1-bit Status Register is used to store the system
status (Table 3).
WIP: Write In Progress status bit; read only.
– WIP = 1 indicates that a high-voltage write cycle is in
progress.
– WIP = 0 indicates that no high-voltage write cycle is
in progress
.
TABLE 1. WIPER COUNTER REGISTER, WCR (8-bit),
WCR[7:0]: Used to store current wiper position
(Volatile, V)
WCR7 WCR6 WCR5 WCR4 WCR3 WCR2 WCR1 WCR0
V
V
V
V
V
V
V
V
(MSB)
(LSB)
.
TABLE 2. DATA REGISTER, DR (8-BIT), DR[7:0]: Used to
store wiper positions or data (Nonvolatile, NV)
BIT 7
NV
MSB
BIT 6
NV
BIT 5
NV
BIT 4
NV
BIT 3
NV
BIT 2
NV
BIT 1
NV
BIT 0
NV
LSB
TABLE 3. STATUS REGISTER, SR (WIP is 1-bit)
WIP
(LSB)
7
FN8174.3
June 23, 2011