CAT5251

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3

PIN DESCRIPTIONS

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.

terminal connections on a mechanical potentiometer.

a mechanical potentiometer.

CS: Chip Select

CS 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 CS after a valid write sequence is what initiates

an internal write cycle.

WP: Write Protect

WP 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

Table 1. PIN DESCRIPTION

Pin #

Name

Function

1

SO

Serial Data Output

2

A0

Device Address, LSB

3

Wiper Terminal for Potentiometer 3

4

High Reference Terminal for

Potentiometer 3

5

Low Reference Terminal for

Potentiometer 3

6

NC

No Connect

7

Supply Voltage

8

Low Reference Terminal for

Potentiometer 0

9

High Reference Terminal for

Potentiometer 0

10

Wiper Terminal for Potentiometer 0

11

CS

Chip Select

12

WP

Write Protection

13

SI

Serial Input

14

A1

Device Address

15

Low Reference Terminal for

Potentiometer 1

16

High Reference Terminal for

Potentiometer 1

17

Wiper Terminal for Potentiometer 1

18

GND

Ground

19

NC

No Connect

20

Wiper Terminal for Potentiometer 2

21

High Reference Terminal for

Potentiometer 2

22

Low Reference Terminal for

Potentiometer 2

23

SCK

Bus Serial Clock

24

HOLD

Hold