X9268TS24Z datasheet(10/22 Pages) RENESAS

10 / 22 page

X9268

FN8172 Rev.4.00

Page 10 of 22

August 29, 2006

DEVICE DESCRIPTION

Wiper Counter Register (WCR)

The X9268 contains two Wiper Counter Registers, one

for each DCP potentiometer. The Wiper Counter

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

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

VVVVVVV

(MSB)

(LSB)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

MSB

LSB

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