CAT5251

© Catalyst Semiconductor, Inc.

7

Doc. No. MD-2017 Rev. F

Characteristics subject to change without notice

INSTRUCTION AND REGISTER

DESCRIPTION

DEVICE TYPE / ADDRESS BYTE

The first byte sent to the CAT5251 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

CAT5251 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

CAT5251 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 tied

address byte must be set to 0.

INSTRUCTION BYTE

The next byte sent to the CAT5251 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 four Wiper

Control Registers. The format is shown in Table 2.

Data Register Selection

Data Register Selected

R1

R0

DR0

0

0

DR1

0

1

DR2

1

0

DR3

1

1

Table 1. Identification Byte Format

Table 2. Instruction Byte Format

ID3

ID2

ID1

ID0

0

0

A1

A0

0101

(MSB)

(LSB)

Device Type

Identifier

Slave Address

I3

I2

I1

I0

R1

R0

P1

P0

(MSB)

(LSB)

Instruction

Data Register

WCR/Pot Selection

Opcode

Selection