CAT5251 datasheet(2/15 Pages) CATALYST

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CAT5251

Doc. No. MD-2017 Rev. F

Characteristics subject to change without notice

PIN DESCRIPTION

SI: Serial Input

SI is the serial data input pin. This pin is used to

input all opcodes, byte addresses and data to be

written to the CAT5251. Input data is latched on the

rising edge of the serial clock.

SO: Serial Output

SO is the serial data output pin. This pin is used to

transfer data out of the CAT5251. During a read

cycle, data is shifted out on the falling edge of the

serial clock.

SCK: Serial Clock

SCK is the serial clock pin. This pin is used to

synchronize

the

communication

between

the

microcontroller and the CAT5251. Opcodes, byte

addresses or data present on the SI pin are latched

on the rising edge of the SCK. Data on the SO pin is

updated on the falling edge of the SCK.

A0, A1: Device Address Inputs

These inputs set the device address when

addressing multiple devices. A total of four devices

can be addressed on a single bus. A match in the

slave address must be made with the address input

in order to initiate communication with the CAT5251.

RH, RL: Resistor End Points

The four sets of RH and RL pins are equivalent to the

terminal

connections

mechanical

potentiometer.

RW: Wiper

The four RW pins are equivalent to the wiper terminal

of a mechanical potentiometer.

¯¯¯: Chip Select

¯¯¯ is the Chip select pin. CS

¯¯¯ low enables the

CAT5251 and CS

¯¯¯ high disables the CAT5251. CS

¯¯¯

high takes the SO output pin to high impedance and

forces the devices into a Standby mode (unless an

internal write operation is underway). The CAT5251

draws ZERO current in the Standby mode. A high to

low transition on CS

¯¯¯ is required prior to any

sequence being initiated. A low to high transition on

¯¯¯ after a valid write sequence is what initiates an

internal write cycle.

¯¯¯: Write Protect

¯¯¯ is the Write Protect pin. The Write Protect pin

will allow normal read/write operations when held

high. When WP

¯¯¯ is tied low, all non-volatile write

operations to the Data registers are inhibited

(change of wiper control register is allowed). WP

¯¯¯

going low while CS

¯¯¯ is still low will interrupt a write to

the registers. If the internal write cycle has already

been initiated, WP

¯¯¯ going low will have no effect on

any write operation.

HOLD

¯¯¯¯¯: Hold

The HOLD

¯¯¯¯¯ pin is used to pause transmission to the

CAT5251 while in the middle of a serial sequence

without having to re-transmit entire sequence at a

later time. To pause, HOLD

¯¯¯¯¯ must be brought low

while SCK is low. The SO pin is in a high impedance

state during the time the part is paused, and

transitions on the SI pins will be ignored. To resume

communication, HOLD

¯¯¯¯¯ is brought high, while SCK is

low. (HOLD

¯¯¯¯¯ should be held high any time this

function is not being used.) HOLD

¯¯¯¯¯ may be tied high

directly to VCC or tied to VCC through a resistor.

PIN DESCRIPTION

Pin #

Name

Function

Serial Data Output

Device Address, LSB

RW3

Wiper Terminal for Potentiometer 3

RH3

High Reference Terminal for

Potentiometer 3

RL3

Low Reference Terminal for

Potentiometer 3

No Connect

VCC

Supply Voltage

RL0

Low Reference Terminal for

Potentiometer 0

RH0

High Reference Terminal for

Potentiometer 0

RW0

Wiper Terminal for Potentiometer 0

¯¯¯

Chip Select

¯¯¯

Write Protection

Serial Input

Device Address

RL1

Low Reference Terminal for

Potentiometer 1

RH1

High Reference Terminal for

Potentiometer 1

RW1

Wiper Terminal for Potentiometer 1

GND

Ground

No Connect

RW2

Wiper Terminal for Potentiometer 2

RH2

High Reference Terminal for

Potentiometer 2

RL2

Low Reference Terminal for

Potentiometer 2

SCK

Bus Serial Clock

HOLD

¯¯¯¯¯

Hold

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