9

FN8172.1

June 21, 2005

DEVICE DESCRIPTION

Wiper Counter Register (WCR)

The X9268 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 X9268 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 (See

Design Considerations Section).

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.

Bit [7:0] are used to store one of the 256 wiper

positions (0~255).

Table 4. Wiper counter Register, WCR (8-bit), WCR[7:0]: Used to store the current wiper position (Volatile, V).

Table 5. Data Register, DR (8-bit), Bit [7:0]: Used to store wiper positions or data (Nonvolatile, NV).

WCR7

WCR6

WCR5

WCR4

WCR3

WCR2

WCR1

WCR0

V

VVVVVVV

(MSB)

(LSB)

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

X9268