X9261 Datasheet, PDF (6/21 Pages) Intersil Corporation – Single Supply/Low Power/256-Tap/SPI Bus

X9261
Figure 1. Detailed Potentiometer Block Diagram
One of Two Potentiometers
SERIAL DATA PATH
SERIAL
BUS
R_H
FROM INTERFACE
INPUT
CIRCUITRY
REGISTER 0
(DR0)
REGISTER 1
(DR1)
C
O
U
8
8
PARALLEL
N
T
BUS
E
INPUT
R
REGISTER 2
(DR2)
REGISTER 3
(DR3)
WIPER
D
COUNTER E
REGISTER ^C
(WCR)
O
D
E
IF WCR = 00[H] THEN R_W = R_L
IF WCR = FF[H] THEN R_W = R_H
UP/DN
INC/DEC
LOGIC
UP/DN
MODIFIED SCK
CLK
R_L
DEVICE DESCRIPTION
Wiper Counter Register (WCR)
The X9261 contains two Wiper Counter Registers, one
for each 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 (See Instruction section for more details).
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 X9261 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 DR0 value into the WCR.
R_W
Data Registers (DR)
Each 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.
6
FN8171.2
September 14, 2005