CAT5261

Doc. No. MD-2122 Rev. E

2

© Catalyst Semiconductor, Inc.

Characteristics subject to change without notice

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 CAT5261. 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 CAT5261.

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 CAT5261. 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 CAT5261.

terminal

connections

on

a

mechanical

potentiometer.

The RW pins are equivalent to the wiper

terminal of a mechanical potentiometer.

CS

¯¯¯: Chip Select

CS

¯¯¯ is the Chip select pin. CS

¯¯¯ low enables

the CAT5261 and CS

¯¯¯ high disables the

CAT5261. 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 CAT5261 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 CAT5261 while in the middle of a serial sequence without

having to retransmit 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

WP

¯¯¯: Write Protect Input

The WP

¯¯¯ pin when tied low prevents non-volatile writes to the device (change of wiper control register is allowed)

and when tied high or left floating normal read/write operations are allowed. See Write Protection on page 6 for

more details.

Pin #

Name

Function

1

SO

Serial Data Output

2

A0

Device Address, LSB

3

NC

No Connect

4

NC

No Connect

5

NC

No Connect

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

NC

No Connect

21

NC

No Connect

22

NC

No Connect

23

SCK

Bus Serial Clock

24

HOLD

¯¯¯¯¯

Hold