CAT5259

© Catalyst Semiconductor, Inc.

9

Doc. No. MD-2000 Rev. H

Characteristics subject to change without notice

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

Table 3. Instruction Set

Instruction Set

Instruction

I3 I2 I1 I0 R1 R0 WCR1/P1 WCR0/P0

Operation

Read Wiper Control

Register

1

0

0

1

0

0

1/0

1/0

Read the contents of the Wiper Control

Register pointed to by P1-P0

Write Wiper Control

Register

1

0

1

0

0

0

1/0

1/0

Write new value to the Wiper Control

Register pointed to by P1-P0

Read Data Register

1

0

1

1

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

1

1

0

0

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

1

1

0

1

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

1

1

1

0

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

0

0

0

1

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

1

0

0

0

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

0

0

1

0

0

0

1/0

1/0

Enable Increment/decrement of the Control

Latch pointed to by P1-P0

Note: 1/0 = data is one or zero.