X9428WPI datasheet(8/20 Pages) XICOR

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X9428

Characteristics subject to change without notice.

8 of 20

REV 1.1.5 7/8/03

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DETAILED OPERATION

The potentiometer has a Wiper Counter Register and

four Data Registers. A detailed discussion of the

Wiper Counter Register

The X9428 contains a Wiper Counter Register. The

Wiper Counter Register 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 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 WCR is a volatile register; that is, its contents are

lost when the X9428 is powered-down. Although the

upon power-up, it should be noted this may be different

from the value present at power-down.

Data Registers

The 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 Wiper Counter Register. It should be

noted all operations changing data in one of these

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, these registers can be

used as regular memory locations that could possibly

store system parameters or user preference data.

Data Registers, (6-Bit), Nonvolatile

Four 6-bit Data Registers for each XDCP. (eight 6-bit

registers in total).

– {D5~D0}: These bits are for general purpose not

volatile data storage or for storage of up to four

different wiper values. The contents of Data Register

0 are automatically moved to the Wiper Counter

Wiper Counter Register, (6-Bit), Volatile

One 6-bit wiper counter register for each XDCP. (Four

6-bit registers in total.)

– {D5~D0}: These bits specify the wiper position of the

respective XDCP. The Wiper Counter Register is

loaded on power-up by the value in Data Register 0.

The contents of the WCR can be loaded from any of

the other Data Register or directly. The contents of

the WCR can be saved in a DR.

(MSB)

(LSB)

WP5

WP4

WP3

WP2

WP1

WP0

VVVVVV

(MSB)

(LSB)

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