X9241A
Figure 7. Acknowledge Response from Receiver
SCL from
Master
1
8
9
Data Output
from Transmitter
Data Output
from Receiver
START
Acknowledge
DETAILED OPERATION
The WCR is a volatile register; that is, its contents are
lost when the X9241A is powered-down. Although the
register is automatically loaded with the value in DR0
upon power-up, it should be noted this may be different
from the value present at power-down.
All four XDCP potentiometers share the serial interface
and share a common architecture. Each potentiometer
is comprised of a resistor array, a Wiper Counter
Register and four Data Registers. A detailed discussion
of the register organization and array operation follows.
Data Registers
Each potentiometer has four nonvolatile Data
Registers. These can be read or written directly by the
host and data can be transferred between any of the
four Data Registers and the WCR. It should be noted all
operations changing data in one of these registers is a
nonvolatile operation and will take a maximum of 10ms.
Wiper Counter Register
The X9241A contains four volatile Wiper Counter
Registers (WCR), one for each XDCP potentiometer.
The WCR can be envisioned as a 6-bit parallel and
serial load counter with its outputs decoded to select
one of sixty-four 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 WCR
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.
If the application does not require storage of multiple
settings for the potentiometer, these registers can be
used as regular memory locations that could possibly
store system parameters or user preference data.
Characteristics subject to change without notice. 7 of 18
REV 1.1.13 12/09/02
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