X9271 Datasheet, PDF (6/23 Pages) Xicor Inc. – Single Digitally-Controlled (XDCP) Potentiometer

X9271
DEVICE DESCRIPTION
Wiper Counter Register (WCR)
The X9271 contains a Wiper Counter Register for the
DCP potentiometer. The Wiper Counter Register can
be envisioned as a 8-bit parallel and serial load
counter with its outputs decoded to select one of 256
switches along its resistor array. The contents of the
WCR can be altered in four ways: it may be written
directly by the host via the Write Wiper Counter
Register instruction (serial load); it may be written
indirectly by transferring the contents of one of four
associated data registers via the XFR Data Register
instruction (parallel load); it can be modified one step
at a time by the Increment/ Decrement instruction.
Finally, it is loaded with the contents of its Data
Register zero (DR0) upon power-up.
The Wiper Counter Register 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
loadings 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. Data can also be transferred between any of the
four Data Registers and the associated Wiper Counter
Register. All operations changing data in one of the
Data Registers is a nonvolatile operation and will 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)
This 1-bit Status Register is used to store the system
status.
WIP: Write In Progress status bit, read only.
– When WIP=1, indicates that high-voltage write cycle
is in progress.
– When 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 the 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
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NV
NV
NV
NV
NV
NV
NV
NV
MSB
LSB
Table 3. Status Register, SR (WIP is 1-bit)
WIP
(LSB)
REV 1.1.7 2/6/03
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Characteristics subject to change without notice. 6 of 23