X9271_14 Datasheet, PDF (5/18 Pages) Intersil Corporation – Single, Digitally Controlled Potentiometer

SERIAL DATA PATH
SERIAL
R_H
FROM INTERFACE
CIRCUITRY
REGISTER 0
(DR0)
REGISTER 1
(DR1)
BUS
INPUT
C
O
U
8
BANK_0 Only
8
PARALLEL
BUS
INPUT
N
T
E
R
REGISTER 2
(DR2)
REGISTER 3
(DR3)
WIPER
COUNTER
REGISTER
(WCR)
D
E
C
O
D
E
INC/DEC
IF WCR = 00[H] THEN R_W = R_L
IF WCR = FF[H] THEN R_W = R_H
LOGIC
UP/DN _UP/DN
MODIFIED SCK _CLK
R_L
R_W
FIGURE 1. DETAILED POTENTIOMETER BLOCK DIAGRAM
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)
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5
FN8174.4
July 18, 2014