9

CAT5259

Document No. 2000, Rev. F

Table 3. Instruction Set

WIPER CONTROL AND DATA REGISTERS

Wiper Control Register (WCR)

The CAT5259 contains four 8-bit Wiper Control Registers,

one for each potentiometer. The Wiper Control Register

output is 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 by the host via Write Wiper

Control Register instruction; it may be written by

transferring the contents of one of four associated Data

Registers via the XFR Data Register instruction, 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 content of its data register

zero (DR0) upon power-up.

The Wiper Control Register is a volatile register that

loses its contents when the CAT5259 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.

Data Registers (DR)

Each potentiometer has four 8-bit non-volatile 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 Control

Register. Any data changes in one of the Data Registers

is a non-volatile 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 standard memory locations for system

parameters or user preference data.

INSTRUCTIONS

Four of the nine instructions are three bytes in length.

These instructions are:

— Read Wiper Control Register - read the current

wiper position of the selected potentiometer in the WCR

— Write Wiper Control Register - change current

wiper position in the WCR of the selected 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 three byte instructions is

illustrated in Figure 8. These three-byte instructions

Note:

1/0 = data is one or zero

Instruction

Instruction Set

Operation

I3

I2

I1

I0

R1

R0

WCR1/

P1

Read Wiper Control

Register

1001

0

0

1/0

1/0

Read the contents of the Wiper Control

Register pointed to by P1-P0

Write Wiper Control Register

1010

0

0

1/0

1/0

Write new value to the Wiper Control

Register pointed to by P1-P0

Read Data Register

1011

1/0

1/0

1/0

1/0

Read the contents of the Data Register

pointed to by P1-P0 and R1-R0

Write Data Register

1100

1/0

1/0

1/0

1/0

Write new value to the Data Register

pointed to by P1-P0 and R1-R0

XFR Data Register to Wiper

Control Register

1101

1/0

1/0

1/0

1/0

Transfer the contents of the Data Register

pointed to by P1-P0 and R1-R0 to its

associated Wiper Control Register

XFR Wiper Control Register

to Data Register

1110

1/0

1/0

1/0

1/0

Transfer the contents of the Wiper Control

Register pointed to by P1-P0 to the Data

Register pointed to by R1-R0

Gang XFR Data Registers

to Wiper Control Registers

0001

1/0

1/0

0

0

Transfer the contents of the Data Registers

pointed to by R1-R0 of all four pots to their

respective Wiper Control Registers

Gang XFR Wiper Control

Registers to Data Register

1000

1/0

1/0

0

0

Transfer the contents of both Wiper Control

Registers to their respective data Registers

pointed to by R1-R0 of all four pots

Increment/Decrement Wiper

Control Register

0010

0

0

1/0

1/0

Enable Increment/decrement of the Control

Latch pointed to by P1-P0

WCR0/

P0