9

FN8168.4

August 30, 2006

The WCR is a volatile register; that is, its contents are

lost when the X9258 is powered-down. Although the

register is automatically loaded with the value in R0

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

different from the value present at power-down.

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.

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.

REGISTER DESCRIPTIONS

Data Registers, (8-Bit), Nonvolatile

Four 8-bit Data Registers for each DCP. (sixteen 8-bit

registers in total).

– {D7~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

register on power-up.

Wiper Counter Register, (8-Bit), Volatile

Instruction Format

Notes: (1) “MACK”/”SACK”: stands for the acknowledge sent by the master/slave.

(2) “A3 ~ A0”: stands for the device addresses sent by the master.

(3) “X”: indicates that it is a “0” for testing purpose but physically it is a “don’t care” condition.

(4) “I”: stands for the increment operation, SDA held high during active SCL phase (high).

(5) “D”: stands for the decrement operation, SDA held low during active SCL phase (high).

Read Wiper Counter Register (WCR)

Write Wiper Counter Register (WCR)

Read Data Register (DR)

WP7 WP6 WP5 WP4 WP3 WP2 WP1 WP0

NV

NV

NV

NV

NV

NV

NV

NV

(MSB)

(LSB)

WP7

WP6 WP5 WP4 WP3 WP2 WP1 WP0

S

T

A

R

T

device type

identifier

device

addresses

S

A

C

K

instruction

opcode

WCR

addresses

S

A

C

K

wiper position

(sent by slave on SDA)

M

A

C

K

S

T

O

P

01 01 A

3

A

2

A

1

A

0

100 100 P

1

P

0

W

P

7

W

P

6

W

P

5

W

P

4

W

P

3

W

P

2

W

P

1

W

P

0

S

T

A

R

T

device type

identifier

device

addresses

S

A

C

K

instruction

opcode

WCR

addresses

S

A

C

K

Data Byte

(sent by master on SDA)

S

A

C

K

S

T

O

P

01 01 A

3

A

2

A

1

A

0

101 000 P

1

P

0

W

P

7

W

P

6

W

P

5

W

P

4

W

P

3

W

P

2

W

P

1

W

P

0

S

T

A

R

T

device type

identifier

device

addresses

S

A

C

K

instruction

opcode

DR and WCR

addresses

S

A

C

K

Data Byte

(sent by slave on SDA)

M

A

C

K

S

T

O

P

0101 A

3

A

2

A

1

A

0

1011 R

1

R

0

P

1

P

0

W

P

7

W

P

6

W

P

5

W

P

4

W

P

3

W

P

2

W

P

1

W

P

0

X9258