6

FN8159.1

March 25, 2005

Five of the seven instructions are four bytes in length. These

instructions are:

• Read Wiper Counter Register – read the current wiper

position of the selected pot,

• Write Wiper Counter Register – change current wiper

position of the selected pot,

• Read Data Register – read the contents of the selected

data register;

• Write Data Register – write a new value to the selected

data register.

• Read Status – This command returns the contents of the

WIP bit which indicates if the internal write cycle is in

progress.

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 wiper to this action will be

delayed by tWRL. A transfer from the WCR (current wiper

position), to a Data Register is a write to nonvolatile memory

and takes a minimum of tWR to complete. The transfer can

occur between the potentiometer and one of its associated

registers. The Read Status Register instruction is the only

unique format (see Figure 4).

Two instructions require a two-byte sequence to complete

(see Figure 2). These instructions transfer data between the

host and the X9111; 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 associated Wiper Counter Register.

• XFR Wiper Counter Register to Data Register – This

transfers the contents of the specified Wiper Counter

Register to the specified associated Data Register.

See Instruction format for more details.

Write in Process (WIP bit)

The contents of the Data Registers are saved to nonvolatile

memory when the CS pin goes from LOW to HIGH after a

complete write sequence is received by the device. The

progress of this internal write operation can be monitored by

a Write In Process bit (WIP). The WIP bit is read with a Read

Status command (see Figure 4).

Power Up and Down Requirements

and the voltages applied to the potentiometer pins provided

are no restrictions on the power-down condition. However,

the datasheet parameters for the DCP do not apply until

ID3 ID2 ID1 ID0

0

A1 A0

I2

I1

I0

RB

RA

SCK

SI

CS

0101

R/W

Device ID

Internal

Instruction

Opcode

Address

Register

0

0

0

0

Address

0

0

FIGURE 2. TWO-BYTE INSTRUCTION SEQUENCE

ID3 ID2 ID1 ID0 0

A0R/W I2

00

SCK

SI

0

0

X X0

0

XX X

W

C

R

9

W

C

R

8

W

C

R

7

W

C

R

6

W

C

R

5

W

C

R

4

W

C

R

3

W

C

R

2

W

C

R

1

W

C

R

0

CS

I1 I0 0 RB RA

0

101

0

XX

X

Device ID

Internal

Address

Instruction

Opcode

Register

Address

Wiper

Position

A1

FIGURE 3. FOUR-BYTE INSTRUCTION SEQUENCE (WRITE OR READ FOR WCR OR DATA REGISTERS)

X9111