8

FN8161.1

March 25, 2005

Table 4. Wiper Control Register, WCR (10-bit), WCR9–WCR0: Used to store the current wiper position (Volatile, V)

Table 5. Data Register, DR (10-bit), Bit 9–Bit 0: Used to store wiper positions or data (Non-Volatile, NV)

Four of the six instructions are four bytes in length.

These instructions are:

– Read Wiper Counter Register – read the current

wiper position of the potentiometer,

– Write Wiper Counter Register – change current

wiper position of the potentiometer,

– Read Data Register – read the contents of the

selected Data Register;

– Write Data Register – write a new value to the

selected Data Register.

The basic sequence of the four byte instructions is

illustrated in Figure 3. These four-byte instructions

exchange data between the WCR and one of the Data

Registers. A transfer from a data register to a WCR is

essentially a write to a static RAM, with the static RAM

controlling the wiper position. The response of the

from the WCR (current wiper position), to a data

register is a write to nonvolatile memory and takes a

between the potentiometer and one of its associated

registers.

Two instructions (see Figure 4) require a two-byte

sequence to complete. These instructions transfer

data between the host and the X9118; either between

the host and one of the Data Registers or directly

between the host and the Wiper Counter Register.

These instructions are:

– XFR Data Register to Wiper Counter Register –

This transfers the contents of one specified Data

Register to the Wiper Counter Register.

– XFR Wiper Counter Register to Data Register –

This transfers the contents of the specified Wiper

Counter Register to the specified Data Register.

See Instruction format for more details.

Other

At all times, the V+ voltage must be greater than or

V- must reach their final values with 1msec of each

other.

Figure 3. Two-Byte Instruction Sequence

WCR9

WCR8

WCR7

WCR6

WCR5

WCR4

WCR3

WCR2

WCR1

WCR0

VVVVVVVVVV

(MSB)

(LSB)

Bit 9Bit 8Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0

NV

NV

NV

NV

NV

NV

NV

NV

NV

NV

MSB

LSB

S

T

A

R

T

01

0

1

0A1

A0 R/W

A

C

K

I2

I1

I0

0

RBRA0

A

C

K

SCL

SDA

S

T

O

P

0

00

ID3 ID2 ID1 ID0

Device ID

Internal

Instruction

Opcode

Address

Register

Address

X9118