8

CAT5261

Document No. 2122, Rev. B

INSTRUCTION AND REGISTER

DESCRIPTION

DEVICE TYPE / ADDRESS BYTE

The first byte sent to the CAT5261 from the master/

processor is called the Device Address Byte. The most

significant four bits of the Device Type address are a

device type identifier. These bits for the CAT5261 are

fixed at 0101[B] (refer to Table 1).

The two least significant bits in the slave address byte,

A1 - A0, are the internal slave address and must match

the physical device address which is defined by the state

of the A1 - A0 input pins for the CAT5261 to successfully

continue the command sequence. Only the device which

slave address matches the incoming device address

sent by the master executes the instruction. The A1 - A0

inputs can be actively driven by CMOS input signals or

address byte must be set to 0.

INSTRUCTION BYTE

The next byte sent to the CAT5261 contains the instruction

and register pointer information. The four most significant

bits used provide the instruction opcode I3 - I0. The R1

and R0 bits point to one of the four data registers of each

associated potentiometer. The least two significant bits

point to one of two Wiper Control Registers. The format

is shown in Table 2.

Table 1. Identification Byte Format

ID3

ID2

ID1

ID0

0

0

A1

A0

0101

(MSB)

(LSB)

Device Type

Identifier

Slave Address

Table 2. Instruction Byte Format

I3

I2

I1

I0

R1

R0

P1

P0

(MSB)

(LSB)

Instruction

Data Register

WCR/Pot Selection

Opcode

Selection

Data Register Selection

Data Register Selected

R1

R0

DR0

0

0

DR1

0

1